A Syrian father lost his 9-month-old twins in sarin gas attack, Apr. 2, 2017. (Alaa Alyousef/AP)

Retired general and leading security expert John Allen told The Jerusalem Post that if Syria were to gas Israelis, it would be “virtually regime suicide.”

Backing a recent assessment by a senior Israeli military official, US Secretary of Defense James Mattis told a news conference in Tel Aviv Friday morning that Syria still possesses chemical weapons.

Meeting with his Israeli counterpart, Defense Minister Avigdor Liberman, Mattis said, “There can be no doubt in the international community’s mind that Syria has retained chemical weapons in violation of its agreement and its statement that it had removed them all.” He did not provide further details based on intelligence sources.

“I can say authoritatively they have retained some; it’s a violation of the United Nations Security Council resolutions and it’s going to have to be taken up diplomatically and they would be ill advised to try to use any again. We made that very clear with our strike,” he said.

Liberman also refused to go into specifics, saying, “We have 100 percent information that Assad regime used chemical weapons against rebels,” referring to a sarin gas attack earlier this month that killed at least 90 people, including dozens of children, and wounded many more.

In an interview with The Jerusalem Post, Marine Corps Gen. (ret.) John R. Allen, a leading security expert, said that if Syria gassed Israelis, it would be “virtually regime suicide.”

The former general was the Obama administration’s special envoy in fighting ISIS and on finding security solutions to the Israeli-Palestinian conflict, US commander in Afghanistan, and is currently a distinguished fellow and chairman of security and strategy at the Brookings Institution.

Recent events, such as Assad’s sarin gas attack and the revelation that the regime likely possesses a significant amount of chemical weapons, lessens the chance that Assad would launch such a strike against Israel, Allen said.

“Were Assad to lash out at Israel and the Israeli population with chemical weapons, it would be virtually a suicidal act for his regime. The enormity of the US response would be unprecedented,” he stated.