Geneva: The United States and Russia threw their full weight behind long-delayed Syria peace talks that the UN said finally would be held January 22, though it was not yet clear whether key sponsors of the warring sides would attend.
"We haven't established a list yet," UN and Arab League mediator Lakhdar Brahimi has said.
That left open the participation of Saudi Arabia, seen as a major sponsor the majority Sunni Muslim rebels, and Iran, which steadfastly back the regime of Syrian President Bashar al-Assad, which is dominated by Alawites derived from Islam's Shiite current.
"These two countries will certainly be among the possible participants," Brahimi said after closed-door talks in Geneva with US and Russian officials.
The talks will bring together the Syrian government and the opposition at the negotiating table for the first time since the rebellion against Assad erupted in March 2011.
UN chief Ban Ki-moon announced the date for the long-delayed conference on Syria dubbed 'Geneva II' at UN headquarters in New York.
"At long last and for the first time, the Syrian government and opposition will meet at the negotiating table instead of the battlefield," Ban told reporters.
"The fighting has raged on far too long - with more than 100,000 dead, almost nine million driven from their homes, countless missing and detained, and terrible violations of human rights," Ban said, calling the war the "biggest threat to international peace".
The United States, which has long urged Assad to step down, called the upcoming talks the "best opportunity" to form a new transitional government to lead Syria out of war.
"In order to end the bloodshed and give the Syrian people a chance to meet their long-deferred aspirations, Syria needs new leadership," US Secretary of State John Kerry said in a statement.
He said he recognised "that the obstacles on the road to a political solution are many, and we will enter the Geneva conference on Syria with our eyes wide open."
Russia, which broadly supports the survival of Assad's regime, also underlined the importance of the talks.