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Washington: The United States welcomed the UN peace plan for Syria, calling it a "milestone" in the efforts to end the conflict.
US Secretary of State John Kerry said the plan gave Syrians a "real choice... between war and peace".
However, disagreements remain over President Assad and the unanimously agreed Security Council resolution makes no mention of his future role.
Western countries have called for his departure, but Russia and China say he should not be required to leave power as a precondition for peace talks.
Kerry said that Assad had "lost the ability to unite the country".
But he also said that demanding Assad's immediate departure was "prolonging the war".
"We are under no illusions about the obstacles that exist," Kerry said. "There obviously remain sharp differences within the international community, especially about the future of President Assad."
However, while Western and Arab nations accept that Assad can be part of the transition, they insist he must be gone at the end of it.
France's Foreign Minister Laurent Fabius said the idea of Assad standing in elections was "unacceptable".
British Foreign Secretary Philip Hammond said it would be "impossible to bring peace and unity while he remains".
But Syria's UN ambassador Bashar Jaafari said there was a "glaring contradiction" between outside countries talking about letting Syrians decide their future yet also insisting on replacing Assad.
The resolution foresees talks between the Syrian government and opposition in early January.
Russian Foreign Minister Sergei Lavrov said it would be possible to reach an agreement on a unity government for Syria within six months.
The plan sets out a timetable for UN-supervised elections within 18 months, and stresses that the Syrian people will decide the future of their country.
The plan also calls for a ceasefire, but there is also disagreement over which armed groups should be designated as terrorists and consequently excluded from any talks or ceasefire.
The agreement demands that all parties cease attacks against civilians.
The Syrian war, which is heading towards its fifth year, has killed more than 250,000 people and displaced millions more, the UN says.
QNA
