TEL AVIV: US Defense Secretary Jim Mattis said Friday that Syria had dispersed its warplanes in recent days and that it retained chemical weapons, an issue he said would have to be taken up diplomatically.

The US launched dozens of missiles earlier this month against a Syrian air base in response to a chemical attack. It said the Syrian regime launched the attack from the Shayrat air base.

The Pentagon has said that the strike had damaged or destroyed about 20 percent of the Syrian military’s operational aircraft.

During a press conference alongside his Israeli counterpart, Mattis was asked whether the Syrian military had moved warplanes to a Russian base in Latakia.

“They have dispersed their aircraft, no doubt. They have dispersed their aircraft in recent days,” Mattis said.

Mattis also reiterated that the US believed Syria had retained some chemical weapons.

“The bottom line is, I can say authoritatively they have retained some (chemical weapons). It’s a violation of the UN Security Council resolutions, and it’s going to have to be taken up diplomatically, and they’d be ill-advised to try to use any again. We’ve made that very clear with our strike,” Mattis said.

The Organization for the Prohibition of Chemical Weapons, a global watchdog, said sarin or a similar banned toxin was used in the April 4 strike in Idlib, Syria.