A UN-backed roadmap to end the Syrian war was met with scepticism Saturday by members of the country's fractured opposition who insist President Bashar al-Assad must go to achieve peace, AFP reports.

The US and Russian initiative, unanimously approved by the UN Security Council on Friday, foresees talks between the rebels and the regime and a rapid ceasefire, perhaps even next month.

But the plan was described as unrealistic by the Istanbul-based National Coalition, the main Syrian opposition grouping.