Russia's Foreign Minister Sergei Lavrov on Tuesday said Moscow was ready to coordinate with a Kurdish-Arab alliance and the US-led coalition in an assault on the "Islamic State" (ISIS) terrorist group's Syrian bastion of Raqa, AFP reports.

"I say with all authority that we are ready for such coordination," Lavrov told journalists at a summit in Uzbekistan, quoted by TASS state news agency.

 He was speaking before Kurdish-Arab forces announced that the assault had been launched, saying: "I cannot say how realistic the reports are that such actions have already started."