Bloomberg in its article titled, "U.S. Warns Russia It Will Hit Assad If He Uses Chemical Arms, Sources Say," claims:
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 al-Assad may be preparing to use chemical weapons to recapture the northwestern province of Idlib from rebels.The article also claimed:
In April 2017, and again a year later, the U.S. carried out limited airstrikes on Syrian targets as punishment for what it said was the use of chemical weapons. Bolton said any U.S. action will be stronger this time, the people familiar with the talks said.However, not only has the US failed categorically to produce the evidence it claimed to possess regarding previous alleged chemical weapon attacks blamed on Damascus, it has also failed to provide any logical motive to explain why Damascus would carry out such attacks.
Comment: Things will be coming to a head in Syria, one way or another, probably quite soon: