The US Secretary of State John Kerry, says Syrian peace talks planned for January are the "best opportunity" to form a transitional government, the BBC reports.
He was speaking shortly after UN Secretary General Ban Ki-moon announced that Syria's government and opposition would meet on 22 January in Geneva.
The UN, US and Russia have been trying for months to get both sides to agree a political solution to the conflict. But the Syrian opposition is divided over which groups should represent it in Geneva, while the opposition insists President Bashar al-Assad must resign.