US Secretary of State John Kerry began talks with Gulf states in Qatar on Monday, seeking to convince them of the merits of last month's nuclear deal with Iran and to discuss the battle against Islamic State militants and the war in Syria.

Most Gulf Arab states are worried that Iran's July 14 accord with the United States and other powers will hasten detente between Teheran and Washington and embolden Iran to support paramilitary allies in the region.

Last month, world powers agreed to lift sanctions on Iran in return for curbs on a nuclear program the West suspects was aimed at creating an atomic bomb, but which Teheran says was peaceful.