Moscow (AFP) - Russian Foreign Minister Sergei Lavrov on Wednesday claimed that Syrian rebels were planning to stage a chemical attack to give the US-led coalition a pretext to strike Damascus.

Lavrov's claims came after he and the Russian military warned Tuesday that any such strike by the US coalition would lead to Russiam retaliatory steps in Syria and "very serious" consequences.

They spoke after US Ambassador Nikki Haley warned that the United States was ready to act in Syria "if we must" to address the use of chemical weapons and "inhuman suffering".

"New provocations with the use of chemical weapons are being prepared -- performances will be organised in Eastern Ghouta, among others," Lavrov told reporters on Wednesday.

"Under this pretext there are plans to use force by the US coalition including against the Syrian capital," he said, adding that he hoped "such irresponsible plans will not be realised".

Lavrov's remarks follow a statement by the chief of the General Staff Valery Gerasimov who on Tuesday raised the spectre of a direct clash between Russian and US troops in Syria.

Gerasimov claimed that Moscow had "reliable information that fighters are preparing to stage the use by government troops of chemical weapons against the civilian population".

He alleged that the US plans to accuse Assad's troops of using chemical weapons against civilians and then "carry out a bombing attack" on Damascus.

He warned Russia would "take retaliatory measures" if the US targeted areas where its military are staying in the Syrian capital.

"Russian military advisers, representatives of the Centre for Reconciliation and members of military police" are currently in the Syrian capital, Gerasimov said.

The Syrian government has repeatedly denied using chemical weapons and Russia, its ally in the war, has questioned UN findings that Damascus carried out sarin and chlorine attacks.

Syrian President Bashar al-Assad and his supporters have consistently claimed that chemical and other attacks were in fact staged, and that an army of actors including children has been trained to fake injury on a massive scale.

Gerasimov's comments came after Russian President Vladimir Putin told the American network NBC in an interview released last week that "we know about fighters' plans to stage the use of chemical weapons by the Syrian army".

Putin insisted that the Syrian government has "long ago" destroyed its stockpiles of chemical weapons and dismissed accusations against Assad and Russia.