The international envoy for Syria, Lakhdar Brahimi, will hold three-way talks with US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov in Geneva on Friday, the United Nations said.

"There will be a tripartite meeting at the Palais des Nations ... starting at 9:30 a.m, (0730 GMT)," the UN said in a statement.

Kerry and Lavrov opened talks in the Swiss city on Thursday on putting Syria's chemical weapons under international control, but differences emerged at the outset over US threats of a military strike.

Brahimi, who the UN said was expected to address the media later on Friday, has been trying to convene an international conference, known as Geneva 2, to broker a political solution to the Syrian crisis. Brahimi met separately on Thursday with Kerry. It was not clear if Brahimi planned to hold one-on-one talks with Lavrov on Friday.