ABDUL-JABBAR: I think all -- the NBA has to do now is just keep the issue in people's minds when it's appropriate. It's not something you can constantly be harping on, but when it's appropriate and they see people doing things that don't line up with how we're supposed to be feeling about things, then people have to speak up. It's -- got to keep you -- it's like watching the temperature. You know, somebody gets a temperature something might be wrong, you've got to deal with it quickly.
STEPHANOPOULOS: And you spoke up this week. Kareem Abdul Jabbar, thanks very much.
ABDUL-JABBAR: Pleasure talking to you.
STEPHANOPOULOS: We're going to turn now to the crisis in Ukraine. Another dramatic escalation overnight, some of the worst violence since the conflict began. And new fears that Putin will invade.
ABC's Muhammad Lila is in eastern Ukraine with the latest.
MUHAMMED LILA, ABC NEWS CORRESPONDENT: It's the most dramatic escalation of violence since the crisis began. Overnight, Ukrainian tanks and troops moving into the town of Kramatorsk held by pro-Russian separatists. Just hours earlier, this woman there telling us, "I feel terrible. I'm in my own country and my own army is taking action against me."
In the country's east, the Ukrainian government admits its already lost control. Pro-Russian militants have swept through nearly every town. This, after demonstrators set fire to a pro-Russian separatist headquarters. At least 31 people dead, most of them burned alive.
The fighting now so serious, overnight America's former ambassador to Moscow admitting this is real, this is war.
600 American troops are being sent to neighboring countries in case of a wider conflict. Meanwhile, as we've seen firsthand, pro-Russian checkpoints are popping up everywhere. The commander here making the threat obvious.
What he's told us is that he can't guarantee our safety if we cross this checkpoint. So we're taking a risk if we go through.
The question now, what will it take for all of this violence to come to an end.
Ukraine's acting prime minister says we're now in the most dangerous 10 days of this conflict. Vladimir Putin is demanding that Ukrainian troops retreat. And on the ground, separatists say they will go ahead with a referendum in exactly one week. And George, if they vote for independence, there's no telling what will happen next.
STEPHANOPOULOS: And thank Muhammad Lila for that.
Let's bring in our chief global affairs correspondent Martha Raddatz, our chief white house correspondent Jon Karl at the White House this morning. And Martha, let me begin with you, that comment from the former U.S. ambassador Michael McFaul, this is real, this is war, really striking. And -- but U.S. officials still don't know how far Putin wants to go, does he just want to stir up trouble in Ukraine, or actually invade?
MARTHA RADDATZ, ABC NEWS CORRESPONDENT: They really don't know. But with such a dramatic escalation over the weekend with all of this fighting there has been so much concern about whether this turns into an all-out war.
I was in eastern Europe last week, and I was with the U.S. forces who are training Latvian and Lithuanian troops. The general who was in charge of those exercises said he is very concerned that Russia will go into eastern Ukraine. And George, if that happens I think you will see a lot more troops in our NATO allies in those countries like Lithuania and Latvia.