SCOTT SIMON, HOST:

The cease-fire that was supposed to halt fighting between Russian separatists and the Ukrainian government has not taken hold. Really, it never seems to have started. Shelling and dying has continued this week with both sides insisting the other had violated the cease-fire agreement. Separatist rebels have taken control of the city of Debaltseve, which serves as a key rail hub in Ukraine. Ivo Daalder is the president of the Chicago Council on Global Affairs and the former NATO ambassador. He joins us now. Thanks very much for being with us, Mr. Ambassador.

IVO DAALDER: Oh, it's great to be here.

SIMON: Do you think a cease-fire is even practical?

DAALDER: Well, I think the only way you're going to get a cease-fire is if one side stops shooting because clearly the Russians and the Russian-backed separatists are bent on continuing to fight. They were never interested in the cease-fire in the first place. We saw that in the Minsk negotiations more than a week ago when they refused to have an immediate cease-fire. They wanted to have a delay. So they could take this city of Debaltseve, but we now also see continued fighting in the south near Mariupol and in other parts of the region.

SIMON: You've been saying for some time now that the U.S. and NATO should provide lethal defensive assistance to Ukraine. Would that just throw more guns into a hot stove?

DAALDER: Well, right now only one side is being armed - is being supported. The Russians, even as they were negotiating in Minsk, were pouring in more tanks and artillery systems. So the question is whether the Ukrainians who are being invaded by a neighboring country should have the right to defend themselves? And, presumably, the better they can defend themselves, the higher the cost of continuing the fighting for Russia and for the separatists, the more likely it is that a real political process can be put into place so that we can have a real cease-fire, a real negotiation and, hopefully, a real political solution.

SIMON: And, Mr. Ambassador, what would you say to those Americans who worry that military assistance is a slippery slope that inevitably leads to their kids becoming troops in Ukraine?

DAALDER: Well, I think that is a valid concern. We are certainly not advocating - and I'm not advocating - that we provide large-scale offensive military equipment - tanks or artillery or fighter planes. And we certainly are not advocating putting American boots on the ground. What we are saying is this a country that is being attacked from the outside. It has the right to defend itself and for us to provide the defensive equipment is one way to help them.

SIMON: Mr. Ambassador, did Ukraine essentially give up nuclear weapons on a promise from the West that it would defend Ukraine if it came to that?

DAALDER: Well, it's a - a direct promise is a strong word, but it is - clearly was the case in the early 1990s that Ukraine and indeed Belarus and Kazakhstan gave up nuclear weapons that were on their territory when the Soviet Union dissolved in return for an assurance by the United States, Great Britain and Russia to their territorial integrity, to the respect for their borders, to their political independence and their sovereignty. And an assurance that those three countries would help make sure that that happened. This is what was violated a year ago when Russia annexed Crimea and it is continuing to be violated by the direct Russian involvement in the war in Eastern Ukraine. And the United States and the United Kingdom in particular has signatures of this agreement - have an obligation, it seems to me, to make clear that there is a cost when something like this is violated.

SIMON: Ivo Daalder is president of the Chicago Council on Global Affairs and former U.S. ambassador to NATO. Thank you very much for being with us.

DAALDER: It's my pleasure. Transcript provided by NPR, Copyright NPR.