World Bulletin / News Desk
"We have not yet made any decision to launch military attacks into Syria," Mattis told lawmakers on the House Armed Services committee. "The president has not made that decision."
Asked what worries him most about the possible military action the U.S. might take, Mattis said: "On a strategic level, it's how do we keep this from escalating out of control."
Earlier Thursday, Trump appeared to walk back earlier comments in which he warned Russia to brace for missiles which he said: "will be coming."
"Never said when an attack on Syria would take place. Could be very soon or not so soon at all!" Trump said Thursday on Twitter.
Later, he told reporters a decision will "be made fairly soon."
The White Helmets, a civil defense agency, blamed the Assad regime for a chemical attack Saturday night in the city of Douma in Eastern Ghouta, which it said killed 78 civilians and injured hundreds of others.
Mattis said he believes the suspected chemical attack took place, but said the U.S. is still "looking for the actual evidence." He said the U.S. has "a lot of media and social media indicators that either chlorine or sarin were used."
Mattis put the onus for verification on an Organization on a Prohibition of Chemical Weapons (OPCW) fact-finding team assigned to investigate, saying Washington is trying to get them to the site outside of Damascus within the week.
"As each day goes by, as you know it’s a non-persistent gas, so it becomes more and more difficult to confirm it," he said.
The OPCW team is tasked with determining if a chemical attack took place, but not determining responsibility.
It confirmed its team is on its way to Syria and expects to commence work Saturday.
Russia on Tuesday vetoed a UN Security Council draft text that would have established a new expert body to determine culpability for the suspected chemical attack.
Addressing reporters at the UN, Vassily Nebenzia, Russia's envoy, stressed the foremost priority should be "to avert the danger of war."
"The second priority now is for the OPCW mission to reach Damascus and Douma, and to see what's really happened," he said.