Kerry predicted, in an interview with CNN's Elise Labott, that Russia's presence in Syria means Moscow could find itself in a "complicated" situation that could affect its policy toward the war-torn country and its leader, President Bashar al-Assad.

"If he's going to side with Assad and with Iran and Hezbollah, he's going to have a very serious problem with the Sunni countries in the region," Kerry said of Putin. "That means he ... could very well become a target for those Sunni jihadists."

Kerry went on to explain: "It's an opportunity for us to force this question of how you actually resolve the question of Syria," he said. "And the bottom line is, you cannot resolve it without including the Sunni(s) in a political solution, a political agreement ultimately, and that will mean that you're going to have to have some kind of transition, some kind of timing. Because as long as Assad is there, you simply can't make piece. Period."

Kerry also said that Syrian President Bashar al-Assad must leave as part of an "orderly transition," rather than calling for his immediate ouster, marking a change in the U.S. position.

He added that if Assad left more quickly, it could lead to an "implosion" that would strip the country of any civil life.

"We need to have an orderly transition, a managed transition, so that you don't have a fear for retribution, loss of life, revenge," Kerry said, urging a leadership change over a "reasonable period of time" but declining to be more specific.

Kerry is in New York for the United Nations General Assembly as the U.S. met with leaders from Iran and Cuba as well as Russia.

(CNN)