Russia on Monday rejected Arab and Western calls for a deadline to be set for the Syrian regime's implementation of a peace plan put forward by international mediator Kofi Annan.

"Ultimatums and artificial deadlines rarely help matters," Foreign Minister Sergei Lavrov said while on a visit to the former Soviet nation of Armenia.

Lavrov added that only the UN Security Council, where Russia wields veto power, could put any time restrictions on Syrian President Bashar al-Assad's compliance with the six-point initiative.

"Annan has a Security Council mandate and it is up to the UN Security Council to decide who is complying with this plan and how," he said.

The so-called "Friends of Syria" meeting of Arab and Western nations in Istanbul agreed this weekend to ask the UN to give Assad a deadline to cooperate with Annan's solution to the year-long conflict.

The plan itself demands that Assad pull out his forces from major flashpoint cities and introduce a daily two-hour ceasefire that could let aid workers deliver supplies and treat the thousands of injured civilians.

But it puts forward no time frame in which Assad has to comply.

Lavrov said the peace plan would not work unless rebel forces also agreed to halt fire.

"The demands should be put to all sides of the barricades," Lavrov said.

"We intend to be friends with both sides in Syria," he added in reference to Russia's past support for Assad.