UN aims for Syria roadmap to peace

Syria faces a moment of truth, UN mediator Staffan de Mistura said on Monday as he opened the first of three rounds of peace talks envisaged to negotiate a "clear roadmap" for a future Syria.

De Mistura asked to hear from all sides but said he would have no hesitation in calling in the big powers, led by the United States and Russia, if the talks get bogged down.

"If during these talks and in the next rounds we will see no notice of any willingness to negotiate ... we will bring the issue back to those who have influence, and that is the Russian Federation, the USA ... and to the Security Council," he said.

The talks are the first to be held in more than two years and come amid an unprecedented cessation in hostilities accepted by President Bashar al-Assad's government and most of his foes.

The truce, the first of its kind in a five-year-old war that has killed 250,000 people, has sharply reduced the fighting over the past two weeks, giving rise to hope that this diplomatic initiative will succeed where all previous efforts failed.

The talks must focus on political transition, which is the "mother of all issues", de Mistura said, while separate taskforces would keep tackling humanitarian issues and the cessation of hostilities.

"As far as I know, the only Plan B available is return to war, and to even worse war than we had so far."

All sides attending the talks have committed to a political transition that will follow the war, but Assad and his opponents disagree fundamentally on what that means, including whether the president must leave power.

The first round of talks will end around March 24, followed by a break of 7-10 days, then a second round of at least two weeks before another recess and a third round.

"By then we believe we should have at least a clear roadmap," de Mistura said.

"I'm not saying agreement, but a clear roadmap because that's what Syria is expecting from all of us."