Feb. 2 (UPI) -- Defense Secretary Jim Mattis warned Syria Friday against repeating its use of chemical weapons, hinting that the United States might retaliate again if it did so.
The Syrian government was accused last year of using sarin gas against its own citizens -- an attack that drew a U.S. retaliatory response of 59 Tomahawk cruise missiles into the air field the chemical assault was launched from.
"We're on the record and you all have seen how we reacted to that," Mattis told reporters Friday, adding that Syria would be "ill-advised to go back to violating the chemical convention" -- a reference to a 2013 agreement that had Russia, Syria's largest ally, responsible for removing all chemical weapons from Syria.
There have been increasing reports from Syria that its military has returned to using chemical weapons. Those reports say President Bashar al-Assad's regime is now using chlorine gas, instead of the more sophisticated sarin, which can simply be thrown from a truck.
Mattis said the Pentagon is examining reports from "groups on the ground" to find hard evidence of chemical weapons use.
Two senior U.S. officials warned on Friday that Syria's continued chemical warfare continue could serve as an opening to a chemical attack on the United States, security website The Cipher Brief reported Friday. The officials said Russia is aware of Syria's actions.