Last week an agreement was made among senior diplomats from Russia, the US, the EU and Ukraine on a plan in dealing with the crisis in the city of Donetsk.

Among other things, the deal called on illegal armed groups across Ukraine to leave buildings they have occupied and disarm.

In response, leaders in the self-declared Donetsk People’s Republic demanded the resignation of Kiev’s interim government and said it was pressing ahead with plans for a referendum on independence by May 11th.

Stephen Cohen is a professor emeritus at Princeton and New York Universities. His books include Soviet Fates and Lost Alternatives: From Stalinism to the New Cold War. He is also a regular contributor to the Nation.com.

His latest article, "Cold War Again -- Who's Responsible?" is available now.

Shona Murray caught up with him and started by asking him about his assessment on how things have deteriorated in Ukraine following last November’s decision by ousted president Yanukovich not to sign an EU association agreement…