PARIS — The United States, France and Russia must step up their coordination in striking the Islamic State in Syria after the Paris terrorist attacks, Secretary of State John Kerry said on Tuesday, but he insisted that cooperation cannot begin until there is a cease-fire and a political transition.

Mr. Kerry expressed optimism that a shift in Syria could come within weeks now that the United States and more than a dozen other nations, including Iran and Saudi Arabia, have agreed to a framework to end the crisis there.

That will depend, he said, on the ability of Syrian opposition groups to organize and negotiate with the government of President Bashar al-Assad, and cooperation from Russia and Iran to ease the transition.

“Now, all we need is the beginning of the political process, and the cease-fire goes in place – that’s a gigantic step,” he said in an interview with reporters who were traveling with him.