U.S. Secretary of State John Kerry said the United States would have to negotiate with Syrian President Bashar Assad for a political transition in Syria and was exploring ways with other countries to pressure him into agreeing to talks.

But State Department spokeswoman Marie Harf said later that Kerry, in an interview with CBS News that aired on Sunday, was not specifically referring to Assad. She reiterated that Washington would never negotiate with the Syrian leader.

Harf added: "By necessity, there has always been a need for representatives of the Assad regime to be a part of this process. It has never been and would not be Assad who would negotiate — and the Secretary was not saying that today."