US and Russia may carry out joint air strikes in Syria, says Lavrov

The United States and Russia have agreed to carry out joint air strikes in Syria if a newly agreed ceasefire holds for a week, Russian Foreign Minister Sergei Lavrov said on Friday.

"We will jointly agree on strikes against terrorists to be carried out by the Russian and American air forces. We have agreed on the zones in which these strikes will be carried out," Lavrov said.

"Only the Russian and American air forces will work in these zones," Lavrov said.

Lavrov said that Russia has persuaded its ally, the Syrian government, that its air force will not fly combat missions in areas where the opposition is present - areas which will be delineated by the US and Russia.

The Pentagon warned in a statement following the announcement that any "potential military cooperation" between the US and Russia was contingent on the terms of the truce being "fully met".

The truce, agreed after a day of marathon talks between Lavrov and his US counterpart John Kerry, will come into force on Monday.

The Geneva negotiating session, which lasted more than 13 hours, underscored the complexity of a conflict that includes myriad militant groups, shifting alliances and the rival interests of the United States and Russia, Saudi Arabia and Iran, and Turkey and the Kurds, the Globe & Mail said.

The Americans and their allies have insisted that Syrian government forces, accused of widespread civilian massacres, must stand down, the WMOT website reported.

Kerry said he believed the plan could lead to talks to "stop the conflict", which has raged for more than five years, killing more than 400,000 and displacing millions.

On the peace talks, however, the gaps remain vast, WMOT said. The main Syrian opposition group reiterated in London this week that they will insist in negotiations that Assad must step down within six months of a transitional process beginning. Assad and his allies are equally insistent that he must remain in power.