"We have to negotiate in the end," Kerry said in an interview with CBS News on Sunday.

"We've always been willing to negotiate in the context of the Geneva I process," he said.

The top US diplomat said his country is looking for steps to bring the Syrian president to the negotiation table.

"What we're pushing for is to get him (Assad) to come and do that, and it may require that there be increased pressure on him of various kinds in order to do that," Kerry said.

"We've made it very clear to people that we are looking at increased steps that can help bring about that pressure," he added.

Kerry also said he is convinced that there will be increased pressure on President Assad with the efforts of US allies and other countries.

The new remarks were made despite earlier comments by the Obama administration’s officials over the Syrian president’s ouster.

American officials had repeatedly announced that the future political system of the Middle Eastern country should not include Assad.

Earlier this week, the United States once again called on the Syrian president to step down and accused his government of being authoritarian and brutal against the Syrian people.

“For four years the Assad regime has answered Syrians’ calls for freedom and reform with unrelenting brutality, authoritarianism and destruction,” State Department spokeswoman Jen Psaki said on Thursday.