Lavrov and Kerry announced in May that their nations would seek to bring Syrian government and opposition representatives together at an international conference, but no date has been set and Moscow says rebel recalcitrance is the main hurdle.

“It is necessary to first convince the opposition (to attend). But maybe it’s time to start using a different verb – to force the opposition to take part in the conference,” Lavrov said after talks with Egyptian Foreign Minister Nabil Fahmy.

Lavrov took issue with what he said were calls from Europe for swift passage of a U.N. Security Council resolution under Chapter VII of the U.N. Charter, which can include the use of force, saying they showed a “lack of understanding” of the U.S.-Russian agreement on chemical arms.