NOEL KING, HOST:
How worried is the U.S. about a potential Russian invasion of Ukraine? President Biden will talk to Ukraine's president, Volodymyr Zelenskyy, later today. Earlier this week, he talked to Russia's president, Vladimir Putin. And in that call, Biden says he told Putin, effectively, don't do it.
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PRESIDENT JOE BIDEN: I was very straightforward. There were no minced words. It was polite, but I made it very clear. If, in fact, he invades Ukraine, there will be severe consequences, severe consequences, economic consequences like none he's ever seen or ever have been seen.
KING: Tough words. Biden also says his administration is planning a conference among the U.S., Russia and some NATO allies. NPR's Pentagon correspondent Tom Bowman is following this one. Good morning, Tom.
TOM BOWMAN, BYLINE: Hey, Noel.
KING: OK. So lots of phone calls, now plans for a conference. Is the point of the conference to just convince Putin not to invade Ukraine?
BOWMAN: You know, I think so - maybe a face-saving way to address Russian concerns about being surrounded by NATO countries, worries about war exercises close to Russia. National Security Adviser Jake Sullivan says he doesn't think Putin has decided whether to invade. Another U.S. official I spoke with says the chances are 50-50. They're seeing troop buildup but not significant logistics buildup - things like food, fuel and ammunition stores. It would signify a likely invasion.
KING: OK. So we just don't know yet. The president, in the meantime, says sending American troops to Ukraine is not an option, is not on the table at this moment. Correct me if I'm wrong. There are already U.S. troops in Ukraine, aren't there?
BOWMAN: That's right. The president was talking about combat troops. There are hundreds of U.S. military trainers there now and have been rotating in since 2015 to provide more expertise to the Ukrainian military. Right now, you have members of the Florida National Guard, as well as special operations forces. And the U.S. is providing some defensive weaponry as well, again, for years - radar systems, equipment that can take out drones and also anti-tank weapons. Biden and others on Capitol Hill have said that aid could increase if Putin invades.
KING: If Putin does invade, what are some scenarios that you are hearing about? How might this play out?
BOWMAN: Well, there are mixed views on what could happen. Some say he could seize the entire country. Others say it's possible he could just grab a portion of land that would connect the Donbas region in the east, where you have Russian separatists, and connect that area with Crimea, the part of Ukraine seized by Russia in 2014. That connection, analysts say, would include the coast along the Black Sea, where there are two shipyards Putin would like to possess. But again, right now, at best, 50-50 chance of an invasion early next year, when frozen ground makes it better for tanks and armor. And again, this could all be just bluster by Putin to get NATO to sit down and talk.
KING: NATO will be at this conference. Some NATO members will be at this conference. We know that Ukraine has been pushing for NATO membership for a very long time. Does Ukraine still want it?
BOWMAN: They do want it. But - and clearly, that would make matters more volatile. Even before the Russian troop buildup on Ukraine's border, NATO leaders were wary of allowing Ukraine to become a member of NATO because, again, it would further inflame Putin.
KING: NPR's Tom Bowman. Thank you, Tom.
BOWMAN: You're welcome. Transcript provided by NPR, Copyright NPR.