VIENNA: US Secretary of State John Kerry is in Vienna for talks with his Russian, Saudi and Turkish counterparts aimed at reviving a moribund effort to resolve Syria's civil war.

Kerry began a day-long series of meetings in the Austrian capital in consultations with the foreign ministers of Saudi Arabia and Turkey, both of whom share the US view that Syrian President Bashar Assad must go for the conflict is to be resolved. They will be joined later by Russian Foreign Minister Sergey Lavrov, whose country is Assad's prime backer.

Friday's meeting follows a surprise visit by Assad to Moscow where he and Russian President Vladimir Putin discussed Russia's military operations in Syria that the US and others say are bolstering Assad and not targeting Islamic State militants as Russia claims.