Russia and the US are discussing “concrete” military coordination to liberate the Isis stronghold of Raqqa, Interfax news agency cited the Russian deputy foreign minister, Oleg Syromolotov, as saying on Wednesday. The revelation follows visits to Moscow this month by the US secretary of state, John Kerry, and CIA head John Brennan.

In a separate development Assad told the Russian news agency RIA he could foresee agreement on a political settlement for Syria within weeks, a timetable that runs ahead of anything that has been discussed in Geneva.