U.S National Security Adviser John Bolton John Bolton on Wednesday (August 22) voiced support for Israeli strikes in recent months on sites in Syria where he said Iranian-supplied missiles and other "threatening weapons" had been deployed.
"I think that's a legitimate act of self-defence on the part of Israel," he said at a news conference in Jerusalem.
Russia, Syrian President Bashar al-Assad's big-power backer, says it is committed to destroying Islamic State insurgents but has been more circumspect about the involvement of Iran, another foreign power reinforcing Damascus.
The Idlib region, a refuge for civilians and rebels displaced from other areas of Syria as well as powerful jihadist forces, was hit by a wave of air strikes and shelling this month, in a possible prelude to a full-scale government offensive.
In April, the Trump administration mustered a coalition of U.S., French and British forces to attack Syrian government facilities related to the production of chemical weapons after a poison gas attack killed dozens of people in Douma district.
Bolton said that the U.S. would respond "very strongly" if chemical weapons were used in Syria.