Russia's partial withdrawal of forces from Syria is "a very positive step", Saudi Arabia's Foreign Minister Adel al-Jubeir said on Wednesday, adding he hoped it would compel President Bashar al-Assad to make concessions.

Saudi Arabia is a leading supporter of the rebels fighting Assad and was aghast at Russia's intervention in support of the Syrian president last year that helped to turn the war in his favour.

"It is our hope that it will contribute to an acceleration of the political process based on the Geneva 1 declaration and that it will compel the Assad regime to make the concessions necessary to bring about a political transition," Jubeir said.

Jubeir's comments, made to Reuters and local state television channels, were Saudi Arabia's first official response to Russian President Vladimir Putin's announcement on Monday of the partial withdrawal of forces.

Asked about oil market speculation of a "grand bargain" involving Saudi energy policy and Russian foreign policy, he said: "As far as I know, and I believe I am in a position to know, there is no such thing."

Saudi Arabia, Russia and some other producers recently agreed to freeze oil production at current levels as a move towards halting the long slide in crude prices since summer 2014 that has greatly reduced energy exporters' income.