The White House accused Russia of attempting to cover up the use of nerve gas by Assad. The report that it issued included information collected by US intelligence to support its claim. The White House press secretary, who speaks for Trump, has altered its story about Syria and the US position. It started our by taking Trump's campaign position that the US would not enter into international conflicts unless its own interests were being threatened. It has gradually escalated, perhaps in response to the global reaction its weak response.
Rex Tillerson is in Moscow today where he will suggest the Putin should back away from Assad. Putin is sticking to his position with Assad and he is claiming that the gas attack was a hoax.