US Secretary of State Hillary Clinton is to hold talks on the ongoing crisis in Syria with Russian Foreign Minister Sergei Lavrov and UN peace envoy Lakhdar Brahimi on Thursday.

US Secretary of State Hillary Clinton is to hold talks on the ongoing crisis in Syria with Russian Foreign Minister Sergei Lavrov and UN peace envoy Lakhdar Brahimi on Thursday.

A senior US State Department official said: “Secretary Clinton has accepted an invitation by UN special envoy Brahimi for a trilateral meeting on Syria this afternoon with Mr Brahimi and Russian FM Lavrov.”

The three-way talks in Dublin come after Clinton on Wednesday renewed Washington's vow to find ways to provide fresh support for the Syrian opposition.

"Now that there is a new opposition formed, we are going to be doing what we can to support that opposition," Clinton told reporters in Brussels, before flying to Ireland.

She warned Damascus that any use of chemical weapons was a “clear red line that must not be crossed.”

"Our concerns are that an increasingly desperate Assad regime might turn to chemical weapons or might lose control of them to one of the many groups that are now operating within Syria," Clinton told reporters after attending her last NATO meeting.

But she again pressed the Assad regime to make "the decision to participate in a political transition, ending the violence against its own people.”

"We hope that they do so because we believe, as you know, that their fall is inevitable. It's just a question of how many people will die until that date occurs."