The "shift" in the positions of Russia and China on Syria should not be underestimated, the spokesman for peace envoy Kofi Annan said on Tuesday after international talks in Geneva.

"Many forces have joined hands here on Saturday ... don't underestimate the degree of a shift that happened particularly in the Russian and Chinese positions to accept the principle of a policy change," Ahmad Fawzi said.

He said reports out of Beijing and Moscow had been "very supportive" of the agreement made at the meeting.

"Let's wait until the dust settles on this agreement and I think everyone will see that it was quite an accomplishment that was achieved here on Saturday."

This included an agreement in principle on a political transition, he said, but a complete halt to the violence was vital first.

"It's imperative that we get a ceasefire," said Fawzi.

He also said exiting the crisis in Syria would not be without its troubles despite agreement at the ministerial meeting.

"It's going to be a long, bumpy road," he said, "but we believe that commitments made in Geneva were genuine and if applied as promised will have an effect on the dynamics on the ground."

World powers agreed a transition plan Saturday with a unity government to include members of the present administration.

Annan convened the crunch talks to try to resurrect his six point peace plan with the help of countries with influence on the regime of President Bashar Al-Assad whose crackdown on the revolt marked the beginning of the crisis in March last year.

Fawzi said the proposals on the table formed a framework for a solution.

"This was a very finely crafted diplomatic document and the solution to the crisis lies therein," he said.

"If you go to the agreed actions that the group members will take to implement the agreement you will see that they have committed to apply joint and sustained pressure on the parties in Syria.

He said Qatar, Iraq, Turkey, Kuwait were among those countries who would exercise their influence on the Syrian parties.

"I think you will understand what kind of leverage they have, what kind of taps can be turned off or on that might influence the behaviour of the parties." he said.

The UN human agency on Tuesday welcomed the Geneva talks, saying the six point plan was the only solution in sight.

"For that to work violence has to stop and the flow of arms also needs to stop," said Rupert Colville, spokesman for the Office of the High Commissioner for Human Rights.

"If the violence doesn't stop on the part of the government forces, the shabhia etc, we can't really expect the flow of arms to stop.

"The two are linked inextricably."