Transcript for 'This Week': Crisis in Ukraine
forward two hours to be on Moscow time. And with Russian troops continuing to mass on the Ukraine border, secretary of state John Kerry will have last ditch di -- diplomacy in Paris with the Russian foreign minister. And terry Moran is there. Good morning. Reporter: The very fact that secretary of state Kerry has flown here for the talks is a good sign. That is because there is so much tension right now, and so much uncertainty on both sides about what the other side might do. And Ukraine remains on a hair trigger. This is the flash point of the world right now. Russian tanks and troops pouring up to the tense border between Russia and Ukraine. Routine military exercises? That's what Russia claims. But at the Pentagon, deep skepticism. We don't have a full knowledge of their intent. But regardless, it does nothing to de-escalate the intention. Reporter: Now there are up to 40 to 50,000 Russian troops along Ukraine's eastern borders. What does Putin want? Across the lands of the former soviet union, there are millions of ethnic Russians, just like in crimea. Putin claims the right to defend all of them, whatever that means. President Obama, in response, is rallying european allies and warning of the dangers of the new Putin doctrine. In the 21st century, the borders of Europe cannot be redrawn with force. Reporter: Fine words, but his real options are limited. The white house has ruled out a military response, and some european leaders are deeply reluctant to impose tough sanctions on Russia that might derail their own fragile economies. So Mr. Obama has tried another tack, belittling Russia all together. Russia is a regional power that is threatening some of its immediate neighbors. Not out of strength, but out of weakness. Reporter: After crimea, some analysts say, that sounds unconvincing. The impression is Putin has flipped the bird to the entire world, and what can the U.S. Do about it? If he were to take eastern Ukraine and southern Ukraine, the U.S. Wouldn't be able to do anything about that. Is that a position of weakness? Reporter: With the talks in Paris, Russia is demanding that Ukraine change its form of government, its constitution to give more autonomy to pro-russian areas. And promise to be non-aligned rather than join Europe. The United States is insisting that only the Ukrainian people can decide that.
This transcript has been automatically generated and may not be 100% accurate.