The U.S. has no evidence to confirm reports from aid groups and others that the Syrian government has used the deadly chemical sarin on its citizens, Defense Secretary Jim Mattis said Friday. “We have other reports from the battlefield from people who claim it’s been used,” Mattis told reporters at the Pentagon. “We do not have evidence of it.” He said he was not rebutting the reports. “We’re looking for evidence of it, since clearly we are dealing with the Assad regime that has used denial and deceit to hide their outlaw actions,” Mattis said. Syrian President Bashar Assad denies...