Mr Kerry was speaking after four hours of talks at the Kremlin with Russian President Vladimir Putin. He said they also agreed to press the Syrian government and rebels to speed up talks on a political transition. A round of indirect peace talks in Geneva between the Syrian government and opposition concluded on Thursday.
UN envoy Staffan de Mistura said he had found a lot of common ground between the two sides. The talks have now gone into a planned recess and Mr de Mistura said they would re-start next month.
Mr Kerry arrived for talks in Moscow 10 days after President Putin announced he was withdrawing the bulk of Russia’s military force from Syria.