The US says it won't fight for Ukraine if Putin invades, but it could still get pulled into a conflict with Russia, experts warn

• The US will not send troops to defend Ukraine if Russia invades, according to experts and ex-diplomats.
• Biden has said the US is not obligated to defend Ukraine because it's not a NATO member.

Russia is banging the war drum on Ukraine's doorstep, as tens of thousands of Russian troops mass along the border raise alarms across the Western world. Europe hasn't faced a crisis on this scale since the days of the Cold War.

Amid rising tensions, the US, in coordination with its allies, has placed 8,500 troops on heightened alert for a potential deployment to eastern Europe, and NATO has sent additional ships and fighter jets to the region as members of the alliance send Ukraine military assistance — including lethal aid.

But in the event Russian President Vladimir Putin gives the order for an invasion of Ukraine, the US and its NATO allies are unlikely to deploy troops in its defense, former US diplomats and experts say. Any US troop deployments would be to NATO countries in the region — not Ukraine — and they'd be sent as a deterrent, meaning they are meant to make Putin think twice about expanding any territorial conquest beyond Ukraine.

"I don't think there is an escalation scenario that leads us to a direct confrontation between the US and Russia in Ukraine," Ivo Daalder, the former US ambassador to NATO, told Insider.

"Anything is possible, of course," he said. "But clearly the intent of the Biden administration and of NATO is not to be military involved directly in a conflict inside Ukraine. ... There's a pretty big line drawn on direct military engagement of US troops or NATO troops."

Still, there is a limited risk that the US could be dragged into the conflict at some point, according to some experts Insider spoke to. A big move by Putin may signal a new era, as their thinking goes, of elevated tensions between Russia and the West, potentially sparking new conflicts. There are also concerns Russian aggression may prompt US responses like sanctions that are so drastic they back Putin in a corner, raising the prospect he may try to broaden his effort.

Daalder said the deployment of US troops to Eastern Europe would be "designed to send the signal to both our allies and the Russians that whatever you're contemplating with Ukraine — don't think that means you could do the same with regard to any NATO country."

Russia has roughly 100,000 troops on Ukraine's border. Comparatively, if the US were to send the far more modest force of 8,500 troops to the region, it would clearly not be meant to provide an offensive capability, Daalder said.

"I do not see US and NATO troops taking military action against Russia should Russia launch an attack on Ukraine," Steven Pifer, the US ambassador to Ukraine from 1998 to 2000, told Insider. "President Biden and NATO Secretary General Stoltenberg, among others, have ruled that out. But you would see a greater flow of military assistance to Ukraine to help the Ukrainians defend themselves."

'While NATO will not intervene in Ukraine, it will defend NATO members'

The US has provided Ukraine with billions in military assistance since 2014, when Russia invaded and annexed Crimea — including $650 million in the past year alone. The Kremlin since 2014 has supported rebels against Ukrainian forces in a war that's estimated to have killed over 13,000 and displaced 1.5 million. Ukraine over that period has received Javelin anti-tank missiles, small arms and ammunition, and patrol boats from the US, among other forms of assistance.

Though Washington maintains strong ties with Kyiv, President Joe Biden in December said that the US is not obligated to defend Ukraine if Russia invades given the country is not a NATO member. "The idea the US will unilaterally use force to confront Russia invading Ukraine is not in the cards right now," Biden told reporters at the time. "We have a moral obligation and a legal obligation to our NATO allies under Article 5. It's a sacred obligation. That obligation does not extend to ... Ukraine."

Article 5 of NATO's charter says that an attack on one member of the alliance is an attack on all. But it's only been invoked once in NATO's history, following the 9/11 terror attacks in the US. Ukraine has sought to join NATO for years and has a robust partnership with the alliance. NATO's expanding influence in Ukraine is among the myriad factors driving Russia's aggressive posture toward its next door neighbor.

Pifer said it's a "sensible move" for the US and NATO to increase their footprint in Eastern Europe, underscoring that Russia recently moved troops into Belarus, a Russian ally — allowing for an "additional corridor of attack against Ukraine" while increasing "Russian military forces near to Poland, Lithuania, and Latvia." All three Baltic countries are NATO members.

"Bolstering forces on NATO's eastern flank would assure nervous allies of NATO's commitment to their defense and remind Moscow that, while NATO will not intervene in Ukraine, it will defend NATO members," Pifer added.

'We're entering into a time when conflicts are probably going to appear more often'

The idea that US troops "will be sent to Ukraine to defend that country against a Russian attack is very clearly off the table," Andrew Lohsen, a Russia expert at the Center for Strategic and International Studies, told Insider.

"American support for Ukraine post-invasion would almost certainly involve providing lethal military assistance. It would be really hard to imagine completely severing ties with Ukraine at a time when they're paying the price for pursuing their dream of Western integration," Lohsen added.

It would hurt US credibility if it pulled back support for Ukraine, Lohsen said, while endorsing sending troops to Eastern Europe as a logical step.

But even though the US and its allies are unlikely to go to war on Ukraine's behalf, an invasion could still trigger "an era of more open confrontation" between Russia and NATO, Lohsen added.

"We are entering into a time when conflicts are probably going to appear more often or could be more deadly because we no longer have agreed rules of what is acceptable behavior," Lohsen said. "This brings us back to an era of expansionist conflicts and basically rewinds the clock."

The US has pushed for a diplomatic resolution to the crisis, but it's failed to produce any major breakthroughs so far. The Kremlin says it has no plans to invade, but the White House continues to warn that Russian action against Ukraine could be imminent.

Meanwhile, Russia has made demands for binding security guarantees, including barring Ukraine from ever joining NATO, that the US and the alliance have repeatedly dismissed as non-starters. The Biden administration has warned Moscow it would face economic consequences on a scale not yet seen if Russia invades.

Jeffrey Edmonds, a former Central Intelligence Agency analyst who's now a Russia expert at CNA, told Insider that he's concerned about a worst case scenario in which the US and its allies respond to a Russian invasion with severe consequences and it creates a level of instability within Russia that would see Moscow "broaden the conflict in order to get us to back down."

"Because then it really has become a conflict between the US and Russia in which Russia thinks we're trying to overthrow the regime," Edmonds added. "There's no holds barred in that kind of conflict."