France’s foreign minister said Western powers are preparing a tough response in case Syrian President Bashar Assad’s regime deploys chemical or biological weapons in its civil war.

Laurent Fabius said “our response … would be massive and blistering.”

Fabius, speaking on RMC radio Monday, said “we are discussing this notably with our American and English partners.” President Barack Obama has called it a “red line” for the US if Assad’s regime were to use chemical or biological weapons.

Fabius says Russia and China are “of the same position,” but acknowledged frustration at their continuing support for Assad.

Syria’s leadership has said it could use chemical or biological weapons if it were attacked from outside. Syria is believed to have nerve agents as well as mustard gas and Scud missiles capable of delivering these lethal chemicals.

On Saturday a senior official in Iran’s Revolutionary Guard Corps threatened to retaliate against any “foolhardy” attack on Syria by the United States or its allies by humiliating the US.

“If the US will do the foolish thing and attack Syria, Iran and Syria’s allies will respond harshly and cause a fiasco for America,” Revolutionary Guard Corps’ deputy chief of culture and propaganda Mahmoud Ali Assoudi said.

The statements were published on an official Iranian government website, but were removed moments thereafter. The BBC’s Persian news service website copied and published the comments before they were taken down.