There is a concerted diplomatic push to end the war, but serious divisions remain
World powers are meeting in New York to try to move forward a tentative plan to bring about a ceasefire in Syria.
Countries on both sides of the conflict are seeking to narrow considerable gaps which stand in the way of progress.These include the fate of Syria's president, which groups could join talks with the regime, and which should be classed as terrorists.
The UN Security Council is expected to later vote on a text backing the broad plan for a truce and negotiations.
It follows a meeting of the so-called International Syrian Support Group (ISSG) which met in Vienna in November and agreed on the parameters of a political plan for the war-torn country.
There, 19 countries, including Syria's allies Russia and Iran, set a target of 1 January for the start of peace talks between the regime and the opposition.
The delegates signed a UN statement calling for a ceasefire to be agreed by 14 May 2016 and for free elections to be held a year later.
The BBC's Barbara Plett Usher in New York says it is the most concrete Syria peace plan yet, with a specific timetable. It is a broad outline, she says, that marks the minimum consensus of countries with a stake in the conflict.
But the process is propelled by a growing conviction that Syria's civil war has to be resolved in order to effectively combat the Islamic State group, our correspondent adds.
Sticking points
Building on the diplomatic momentum, Saudi Arabia, a staunch foe of Syrian President Bashar al-Assad, held a meeting earlier this month of dozens of disparate rebel and Syria opposition groups to try to forge a common approach to possible peace talks.They agreed to a programme of six months of negotiations followed by the formation of a transitional body from which President Assad and his aides would be excluded.
However, Russia, Iran and Syria dismissed the meeting, saying the groups were unrepresentative and unacceptable.
There are still significant areas of disagreement between the two sides in the war and their backers.
One of the major sticking points is which rebel groups should be considered terrorist outfits and consequently excluded from any talks or ceasefire. Jordan has been tasked with drawing up a list.
The Syrian war, which is heading towards its fifth year, has killed more than 250,000 people and displaced nearly 12 million, the UN says.
The United States, which supports the Syrian opposition, wants a negotiated settlement based on the 2012 Geneva Communique, which calls for the formation of a transitional governing body. It says President Bashar al-Assad must go.
Russia, which launched an air campaign against Mr Assad's opponents in September, also calls for the implementation of the Geneva Communique. But it says Mr Assad's future is for the Syrian people, and not external powers, to decide.
Most of Syria's political and armed opposition factions now agree on the need for a managed transition, but they demand that the president leave at the start of it.
Bashar al-Assad says peace talks cannot begin until "terrorism" is eliminated, and that his departure is out of the question before elections are held.
