Defense Secretary James Mattis on Friday warned the Syrian regime to think carefully before using chemical weapons again.
Mattis' threat appeared to be in reference to the U.S. military strikes on a Syrian airfield last April, which were in retaliation for a chemical attack carried out by the regime of Syrian President Bashar al-Assad days earlier, Politico reported.
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"You've all seen how we reacted to that," Mattis said, adding that the Syrian regime "would be ill-advised" to launch more chemical attacks, as some recent reports from inside the country suggest.
Mattis acknowledged those reports and said the Pentagon was looking for evidence to confirm them. "Groups on the ground, NGOs, fighters have said" that the regime has used sarin gas in recent attacks, he said, but "we do not have evidence."
The regime appears to have weaponized chlorine again, Mattis said, but "we are even more concerned about the possibility of sarin use."
"We think that they didn't carry out what they said they'd do" in terms of destroying chemical weapons stores and production capabilities, Mattis added, confirming remarks earlier this week by State Department officials.
Mattis, a retired four-star Marine Corps general, went on to say that Turkey's offensive against Syrian Kurdish militants in Afrin is a "distraction" from the fight against the Islamic State in Syria.
In terms of balancing the interests of Turkey and the Syrian Kurds, Mattis said, "Welcome to the real world."
Mattis said that Turkey has "legitimate security interests" in fighting the Kurdish PKK terrorist group before praising the Kurdish-dominated Syrian Democratic Forces for being the "one group that's proven capable" of helping fight ISIS in Syria.