The US will “have to negotiate” with President Bashar al-Assad and is seeking to force him into peace talks to end the Syrian conflict, according to secretary of state John Kerry.
Now in its fifth year, the conflict has claimed hundreds of thousands of lives and millions have been displaced by the fierce fighting.
The rise of Isis in Syria appears to have led to the US rowing back on their hard-line stance on Assad.
The secretary of state did not repeat the usual US line that the Syrian president had lost all legitimacy and had to go, when interviewed by CBS News on Sunday.
In the past, Washington insisted that Assad must be removed through a negotiated, political transition, but now appears to have shifted slightly from this position.
"We have to negotiate in the end. We've always been willing to negotiate in the context of the Geneva I process," the US’ top diplomat said, referring to a 2012 conference that called for a negotiated transition to end the conflict.
The secretary of state said that there may need to be "increased pressure" on Assad of "various kinds”, to force him to participate in negotiations to end the conflict.
The US led efforts to organise UN-backed peace talks in Geneva failed last year, when discussions between government and opposition representatives collapsed after two rounds. No new talks have scheduled.
"To get the Assad regime to negotiate, we're going to have to make it clear to him that there is a determination by everybody to seek that political outcome and change his calculation about negotiating," Mr Kerry said.
"That's under way right now. And I am convinced that, with the efforts of our allies and others, there will be increased pressure on Assad,” he added.
President Assad looks to be as secure in power now, as at any time during the conflict and has the backing of both Russia and Iran.
Additional reporting by ReutersReuse content