The U.S. and Russia exchanged warnings about a possible chemical attack in Syria and a Western military intervention in response, on the eve of what may be one of the decisive campaigns in the Middle Eastern country's civil war.
Tensions between the nuclear powers flared after National Security Adviser John Bolton told his Russian counterpart, Nikolai Patrushev, that the U.S. has information Syrian President Bashar Assad may be preparing to use chemical weapons to recapture the northwestern province of Idlib from rebels.
The U.S. is ready to respond forcefully, Bolton said during a five-hour meeting in Geneva on Thursday, according to four people familiar with the discussions. Assad's army, with Russian air support, has been mustering troops and tanks around Idlib, the last stronghold of Syrian opposition groups now dominated by jihadis.