Trump Says Syria Decision Coming Soon; Mattis Says U.S. Awaiting Evidence

U.S. is working to have inspectors see if there is evidence of a chemical attack on civilians

WASHINGTON—President Donald Trump said Thursday that a decision would be made “fairly soon” on a U.S. response to a suspected chemical attack by Syrian armed forces.

After Mr. Trump warned in a Twitter message Wednesday that missiles would be launched, he moderated those comments in a subsequent tweet Thursday, saying an attack on Syria “could be very soon or not so soon at all.”

Speaking...