US says it will end joint Syrian work with Russia if Aleppo assault continues

The United States threatened on Wednesday to halt its joint work with Russia on Syria unless Russia moved to end the assault on Aleppo and to restore a defunct ceasefire, the US State Department said on Wednesday.
Secretary of State John Kerry conveyed the message in a call with Russian Foreign Minister Sergei Lavrov in which he voiced "grave concern over the deteriorating situation in Syria" and said Washington holds Moscow responsible for the situation, including the use of incendiary bombs in an urban environment, State Department spokesman John Kirby said in a statement.