The United States yesterday warned the Russian and Syrian governments against chemical weapon use in Syria.

State Department spokeswoman Heather Nauert said the United States "will respond to any verified chemical weapons use in Idlib or elsewhere in Syria ... in a swift and appropriate manner".

The comments came as Russia again accused Syrian rebels of preparing a chemical attack that Moscow said will be used to justify a Western strike against Syrian troops.

Russia's Deputy Foreign Minister Sergei Ripkuk (Ryabkov )said on an al-Qaeda-linked group is preparing the attack in Idlib.

Western countries and independent analysts say Syrian government forces have conducted several chemical weapons attacks over the course of the seven-year civil war. Alleged chemical attacks in 2017 and earlier this year ,led the US to launch punitive strikes against Syrian forces.

The Syrian government denies ever using chemical weapons.

On the other hand ,Damascus has been sending reinforcements towards Idlib for weeks, ahead of an expected attack against the last major rebel stronghold, in the country.