WASHINGTON xe2x80x93xc2xa0President Joe Bidenxc2xa0spoke with Russian President Vladimir Putin for nearly an hour Thursday amid growing concerns over Moscow’s military buildup along the border with Ukraine.xc2xa0

Biden told Putin that the United States and its allies “will respond decisively if Russia further invades Ukraine,xe2x80x9d White House press secretary Jen Psaki said in a statement released after the phone call.xc2xa0

A senior administration official said Biden told Putin he has two options: diplomacy leading to de-escalation or further aggression leading to xe2x80x9cserious costs and consequences.xe2x80x9d

The possible consequences include economic sanctions, adjustments of NATO forces in allied nations and additional assistance to Ukraine to defend its territory, said the official, who briefed reporters on the condition of anonymity.

The White House has repeatedlyxc2xa0warned Russia against invading its neighborxc2xa0xe2x80x94 with a senior administration official labeling the situation a “moment of crisis” Wednesdayxc2xa0xe2x80x94 and Bidenxe2x80x99s call with Putin marked a new test of American diplomacy and leadership.xc2xa0

xe2x80x9cBiden is under pressure to show results and to show whether the United States, with its allies, can deter Russia and get it to step down from this build up,xe2x80x9d said Angela Stent, director of the Center for Eurasian, Russian and East European Studies at Georgetown University.

Biden’s call with Putin lasted roughly 50 minutes, ending at 4:25 p.m. EST, according to the White House.

Russia has ramped up its military presencexc2xa0along Ukraine’s eastern border over the past several months. Biden and America’s Westernxc2xa0allies have said they will impose tough economic sanctions against Russia if its aggression against Ukraine escalates.

Ukraine declaredxc2xa0independencexc2xa0from the former Soviet Union in 1991, and it is now a fledgling democracy with a pro-Western tilt.xc2xa0U.S. foreign policy experts say it is in Americaxe2x80x99s interest to stave off Russian aggression, particularly as Putin looks to rebuild the Soviet empire.

Russia annexed thexc2xa0Crimean peninsulaxc2xa0in 2014, a swath of Ukrainianxc2xa0territory located between the Black Sea and the Sea of Azov. The Kremlin has continued to try to undermine the countryxe2x80x99s sovereignty, militarily and in other ways.

The White House has previously said discussions with Russia would be more productive if Putin withdraws some of thexc2xa0estimated 100,000 Russian troops from Ukraine’s border.xc2xa0However, troop presence has remained consistent, worrying the White House.

What is happening at Ukraine’s border?:Putin’s buildup of Russian troops sparks concern

Biden and Putinxe2x80x99s call camexc2xa0ahead of a bilateral meeting between U.S. and Russian officials scheduled for Jan. 10.xc2xa0That same week, there will also be meetings between NATO and Russia, as well as the Organization for Security and Cooperation in Europe, where Ukraine will be present.

The administration official said Biden viewed his conversation with Putin on Thursday as an opportunity to lay the groundwork for the upcoming January meetings.xc2xa0

xe2x80x9cBoth leaders acknowledged that there were likely to be areas where we could make meaningful progress,xe2x80x9d the official said.

Putin has said he wantsxc2xa0the U.S. and Western allies to not allow Ukraine to join NATO xe2x80x94 a move he argues would pose a threat to Russian security. The Russian leader has also demanded that NATO no longer station troops orxc2xa0military equipment in countries that were formerly part of thexc2xa0Soviet Union.

xe2x80x9cWe have made it clear that any further movement of NATO to the East is unacceptable,xe2x80x9d Putin said at a news conference on Dec. 23. xe2x80x9cIs there anything unclear about this? Are we deploying missiles near the US border? No, we are not. It is the United States that has come to our home with its missiles and is already standing at our doorstep.”xc2xa0

Biden held a high-stakes video teleconference with Putin earlier this month, where he emphasized that he preferred a diplomatic solution to the crisis in Ukraine. However, the president warned that if Russia invades Ukraine, the U.S. would send additional defense resources to Ukraine and would look to deploy additional forces to fortify its NATO allies in the area.

Contributing: Michael Collins, Matthew Brown and Joey Garrison

Reach Rebecca Morin at Twitter @RebeccaMorin_

Moscow has unveiled outlandish security demands which sound aggressive and suggest that it may underestimate both NATO and Ukraine. Although any new Russian invasion could be devastating, they must prepare for the possibility.

The Brezhnev-era Kremlin underestimated the West. In the late 1970s, the USSR began deploying SS-20 theater-range ballistic missiles aimed at Europe and Japan. Despite Moscow’s fierce campaign (PDF) of propaganda, disinformation, and intimidation, NATO responded by deploying in Europe missiles of comparable range. Having failed to scare NATO into submission, hidebound Soviet leaders lost face. Then a liberalizing leader, Mikhail Gorbachev, came to power and agreed with President Ronald Reagan to ban both sides’ missiles.

Soviet leaders in the xe2x80x9cera of stagnationxe2x80x9d may have believed their own false propaganda that the West was weak and disunited. Today’s Kremlin may be making the same mistake.

On December 17, Moscow publicized proposed demands which would in effect require the United States to withdraw from Europe and NATO to collapse. Only a day later, the Kremlin said it might xe2x80x9cup the ante.xe2x80x9d Nonetheless, on December 21 U.S. national security advisor Jake Sullivan said the United States was ready for talks in xe2x80x9cfull coordination with our European allies and partners.xe2x80x9d

In his December 23 press conference, Putin said he had xe2x80x9cso far seen a positive reactionxe2x80x9d to Moscow’s proposals, but satellite photos show that in mid-December Russia was still deploying more tanks, short-range ballistic missiles, and other arms near Ukraine.

Russia’s demands would force the United States to remove its nuclear weapons from Europe and forego deployment of theater-range missiles, even though such weapons could be deployed in European Russia. Proposed accords would ban NATO from admitting any xe2x80x9cformer Soviet republicxe2x80x9d even though NATO has rejected such a ban. They would require that NATO withdraw infrastructure in its eastern members, but the heightened Russian threat to Ukraine may spur NATO to do the opposite. Evidently anxious about popular uprisings against its rule, the Kremlin also demands a ban on xe2x80x9cactions aimed at changing the political or social order.xe2x80x9d

The Kremlin knows how to negotiate constructively, as it did successfully when it achieved the New START Treaty and the Iran nuclear agreement. On December 21, President Vladimir Putin hinted that the purpose of the new unrealistic demands was to help create a justification for war: xe2x80x9cIf our Western counterparts continue a clearly aggressive line, we will undertake proportionate military-technical countermeasures.xe2x80x9d

Thus, NATO might be wise to consider that Russia could launch a wider invasion of Ukraine. Wars always bring uncertainties, but several considerations could be relevant.

First, any attempt to seize a large area east of the Dnipro River, including such cities as Karkhiv, Dnipro, and Odessa, and possibly Kyiv, would pose a major military operational challenge and take time. Looking at a notional scenario of an invasion by 130,000 Russian troops, RAND found that the operation would take xe2x80x9cweeks, if not months, to fully develop and execute.xe2x80x9d And an invasion could meet resistance and incur heavy casualties.

Second, in 2014 Russian invaders faced a disorganized but determined Ukrainian opposition, but this time they would confront a better trained, armed, and motivated fighting force. Even a Russian xe2x80x9cshock and awexe2x80x9d assaultxe2x80x94mass cyber and electronic attacks, and a multi-front combined arms operationxe2x80x94might not easily carry the day.

Ukraine’s defenses could be stressed but still slow invaders. Many Ukrainian commanders and soldiers are battle-hardened from the seven-year war in the Donbas. To reduce risks from drone attacks, some Ukrainian forces could disperse in small squads on ATVs or other mobile platforms. Equipped with precision-guided mortars, guided anti-tank and anti-aircraft missiles, and loitering munitions, mobile forces could frustrate some Russian battle plans.

Third, if Ukraine were at risk of being overrun or if adjacent NATO allies were threatened, NATO might intervene. As in the 1973 Yom Kippur War when Israel was threatened with potential defeat, the United States could airlift military aid. Washington has not provided Stinger anti-aircraft missiles, which could down Russian helicopters and low-flying fixed-wing aircraft, but in an extreme scenario it might do so. Although Biden says that providing U.S. troops is xe2x80x9cnot on the table,xe2x80x9d in compelling circumstances NATO could unleash formidable air and naval power.

Fourth, the Kremlin might be tempted think that fears of a widened war or of attacks by cyber weapons, long-range precision-guided missiles, or even limited use of nonstrategic nuclear forces would deter NATO from intervening militarily. These concerns might be a factor, but the alliance has prepared to respond to aggression with its own tools of coercion. For example, it could mount cyber assaults that disrupt Russia’s economy and financial system and military logistics for its fighters in Ukraine.

Fifth, Ukraine could mount a longer-term insurgency against Russian occupiers, which might be stretched thin or rely partly on ill-trained conscripts. On December 19, The Washington Post said the Biden administration was exploring ways to aid guerillas. An insurgency might be sustainable if Ukraine west of the Dnipro River or an adjacent NATO member state were to be a sanctuary and source of resupply. At the same time, Russian reactions to armed resistance could be xe2x80x9cswift, direct, and brutal.xe2x80x9d

The Kremlin may err if it thinks Ukraine or NATO would easily submit to aggression. The hour is late, but Kremlin leaders might consider instead seeking a stable European security architecture that protects Russia’s interests while also allowing for a vibrant and sovereign Ukraine.

William Courtney is an adjunct senior fellow at the nonprofit, nonpartisan RAND Corporation, and was U.S. Ambassador to Kazakhstan, Georgia, and a U.S.-Soviet commission to implement the Threshold Test Ban Treaty. Peter A. Wilson is an adjunct international/defense researcher at RAND.

This commentary originally appeared on Moscow Times on December 27, 2021. Commentary gives RAND researchers a platform to convey insights based on their professional expertise and often on their peer-reviewed research and analysis.

DENVER xe2x80x93 A Colorado police officer and a tattoo shop employee were in the hospital Thursday after a gunman injured them and fatally shot five others in a Denver-area killing spree that he foreshadowed in a dark series of self-published books.

Ashley Ferris, a three-year veteran of the Lakewood Police Department, underwent surgery at a local hospital and was in stable condition, surrounded by family, police said. Ferris confronted the gunmanxc2xa0Monday evening in a busy Lakewood shopping district, where he shot her in the abdomen.xc2xa0Ferris, on the ground, fired back, killing the man.

“All of us at the Lakewood Police Department are incredibly proud of Agent Ferris and the bravery shown by her and her fellow law enforcement officers during this active shooter situation,” Lakewood Police Chief Dan McCasky said in a statement Wednesday evening. “The entire Lakewood family will be here to support Agent Ferris and her family as she embarks on this recovery process.”

DENVER SHOOTING:Company published series of books that mirrored deadly rampage, named 2 victims

Jimmy Maldonado, a piercer at one of thexc2xa0tattoo shops targeted in the attack,xc2xa0was shot in the neck and shoulder area and remains in the hospital, he told the Denver Gazette on Wednesday.

His wife, former yoga instructor Alyssa Gunn Maldonado, 35, was killed in the shooting, along with four other people: tattoo artists Alicia Cardenas, 44, and Danny Schofield, 38;xc2xa0hotel clerk Sarah Steck, 28; and Michael Swinyard, 67.

Two of the shooter’s victims were named in a series of books published by a company he once owned. Authorities on Tuesday identified the gunman as Lyndon James McLeod, 47.

According to Colorado state business records, McLeod was the owner of Flat Black Ink, a Denver business that opened in 2005, was declared delinquent in 2017 and was listed as having a name change in 2018.

A business by the same name published a series of three books fromxc2xa02018 toxc2xa02020, according to an Amazon listing for the series and a Patreon link to an audiobook version, which were taken down Wednesday.

In the books, a main character named “Lyndon James MacLeod” brutally murders people inside a tattoo parlor along the same street as one of the shootings Monday, as well as a man named Michael Swinyard inxc2xa0a condo building near Denver’s Cheesman Park, where another of the shootings happened, according to a USA TODAY review of the books.

The character alsomurders a woman named Alicia Cardenas. He targets two more people with the same first names of two employees of Cardenas’ tattoo parlor, as well as a man with the same full name as another Denver-area tattoo artist who wasn’t killed in the attacks. The book also includes characters identified only as “Sarah” and “Danny.”

One of the tattoo parlors targeted in the shooting, World Tattoo Studio,xc2xa0now operates at the same Denver address listed for Flat Black Ink. World Tattoo owner Ian Lxc3xbctz told USA TODAY that one of the victims, Cardenas, previously owned the shop.

Denver Police are “aware” of the book series, which has become “a component of our ongoing homicide investigation,” the department told USA TODAY in a statement Wednesday.

McLeod was known to law enforcement and officers investigated him fromxc2xa0mid-2020 toxc2xa0early 2021, Denver Police Chief Paul Pazen told reportersxc2xa0Tuesday. Neither investigation resulted in criminal charges, Pazen said. He would not give further details about the incidents.

McLeod had “personal” or “business” relationships with nearly all of the victims and “was targeting specific people,” Matt Clark, Denver police commander of the Major Crimes Division, said.

The incidentsxc2xa0erupted Monday evening in Denver, Clark said, when the gunman fatally shot Gunn Maldonado and Cardenas and wounded Maldonado inside Sol Tribe Tattoo & Piercing. Maldonado hid under a car in a parking lot after he was shot, he told the Denver Gazette.

Minutes later, at an address at or near another tattoo parlor, World Tattoo Studio, McLeod shot at people inside a hybrid residence-business, but no one was injured, Clark said. He then set a van on fire in the alley behind the business, Clark said.

Police received a call about the shooting, then another call minutes later, Clark said, after McLeod fatally shot Swinyard in his residence at One Cheesman Park.

McLeod was dressed as “a police officer in tactical gear with a police logo and badge and carrying a rifle” when he entered the lobby of the condo building, according toxc2xa0an email sent from property management to residents and obtained by USA TODAY.

Building manager Joshua Schroeder, who signed the email, did not immediately respond to a request for comment. Asked about the email, axc2xa0spokesperson for Denver police said the department was “unable to provide further details” about the investigation.

Officers located McLeod minutes after he shot Swinyard and exchanged gunfire, but McLeod disabled the officers’ car and took off onto the highway, Clark said.

McLeod drove to Lakewood and fatally shot Schofield inside Lucky 13 Tattoo & Piercing, Lakewood Police spokesman John Romero said.

Romero said Lakewood police agents later found McLeod’s vehicle near or at a Wells Fargo bank in a busy shopping district, and officers exchanged gunfire before McLeod fled. The gunman then entered a nearby restaurant, where he threatened people with a gun but did not fire any shots or injure anyone, Romero said.

McLeod went around the corner to the nearby Hyatt House hotel, walked inside, had a “brief conversation” with the front desk worker, Steck, and shot her several times, Romero said.

Less than two minutes later, McLeod was walking through a shopping center when he encountered Ferris.

Steck, who worked at the Hyatt, was taken to the hospital Monday and died from her injuries Tuesday, police said. Police said McLeod had “previous interactions with the hotel” but not Steck, specifically.

Travis Leiker, president of Capitol Hill United Neighborhoods, told USA TODAY he was in a meeting at his organizationxe2x80x99s office and community center next to One Cheesman Parkxc2xa0when he heard the gunshots Monday.

“I heard a pop, pop, pop,” Leiker said. First responders arrived within minutes and later taped off the area, Leiker said.

“The mood in Denver is of shock and concern,” he said. “There is a feeling of not being safe in our neighborhoods.”

Leiker said he was recently informed of the existence of McLeodxe2x80x99s books from a reporter. Leiker said it was strange to read the gunmanxe2x80x99s detailed description of the alleyway between the condo building and his organizationxe2x80x99s community center.

He said it was “abundantly clear”xc2xa0there was a “breakdown of communication” between law enforcement and residents and that residents should have been informed of the “looming threat.”

“Why or how were specific people named in a manifesto and properties, including our own, were cased as part of this writing and none of us knew anything about it?”xc2xa0Leiker said.

Members of the Colorado tattooing and body piercing community said they were shocked by the shootings and grieving the losses of beloved friends and colleagues. Several described Cardenas,xc2xa0one of the victims, as a groundbreaker who paved the way for women and people of color in the industry.

Cardenas was a tattooer, mural artist and cultural anthropologist who owned Sol Tribe Tattoo & Piercing, according to the shop’s website. The website describes Cardenas as a “true Denver Native” and a “proud Indigenous artist.” She is survived by her 12-year-old daughter.

Maldonadoxc2xa0is an Aztec dancer and Denver activist who works as a piercer at Sol Tribe, according to the shop’s website.xc2xa0His late wife,xc2xa0Gunn Maldonado,xc2xa0taught yoga at Sol Shine in Denver, according to a post on its Facebook page. She also said on her Instagram that she was a doula in Denver.

Schofield, another fatal victim, was a tattoo artist and Colorado native, according to the Lucky 13 website. He had been tattooing for about 15 years, according to the site. He was also known as Dano Blair. Schofield leaves behind three young children.

The Lakewood Police Department said it was setting up a resource center Thursday for anyone “affected by the senseless tragedy.” Trauma resources and mental health therapists would be available across from the Hyatt House, where Steck was killed, police said.

Denver and Lakewood police were also encouraging people to donate to a Colorado Healing Fund for the victims of the shootings. The fund was founded in 2018 in an effort to contribute to victims of mass casualty crimes in Colorado.

Monday’s rampage was the 13th mass shooting in Colorado this year, according to the Gun Violence Archive, a nonprofit that tracks gun violence nationally using a combination of police statistics and media reports. The archive defines a mass shooting as four or more people shot, not including the shooter, at the same general time and location.

Contributing: Bill Keveney, USA TODAY