Mattis: U.S. Concerned Sarin Gas Used in Syria

The United States is concerned that sarin gas may have been recently used in Syria, U.S. Defense Secretary Jim Mattis said Friday, as Washington steps up the pressure on Bashar al-Assad's regime to put an end to chemical attacks.

Mattis told reporters that chlorine gas was known to have been weaponized "repeatedly" in attacks in Syria, but added: "We are even more concerned about the possibility of sarin use, and we are looking for the evidence."

The Pentagon chief cited reports from NGOs and rebel groups in the battlefield who say the chemical weapon has been used, although he stressed that the United States currently has no evidence to support those claims.

"But we are not refuting them -- we are looking for evidence of it since clearly we are dealing with the Assad regime that has used denial and deceit to hide it," he said.

"They would be ill-advised to go back to violating the chemical convention."

Mattis's remarks come a day after senior administration officials said Washington was not ruling out fresh military action against the Syrian regime in the wake of suspected sarin and chlorine attacks.

President Donald Trump "hasn't excluded anything" in the bid to halt the program, a senior U.S. official told AFP. "Using military force is something that is still considered."

There have been more than 260 reports of chemical attacks in Syria, some of which have been verified by UN-backed inspectors and attributed to the Assad regime.

Aside from the threat to Syrian civilians, Washington is worried that the well-documented chemical attacks -- systematically denied by Damascus and its Russian ally -- is undermining long-standing taboos on their use.

The Assad regime appears to have altered course only slightly since the United States fired 59 Tomahawk cruise missiles at a Syrian airfield in 2017, after a large chemical attack on rebel-held Khan Sheikhun.

Instead of dropping barrel bombs filled with chemical agents from helicopters, senior administration officials say that mortars and other ground-based delivery systems are now being used.

The chemical of choice has most often been industrial chlorine, which is easy to produce and legal to possess, rather than sarin, which is banned by the Chemical Weapons Convention.