PARIS — France will not launch an assault on Syria alone and will wait for the US Congress to decide on whether to punish President Bashar al-Assad's government for a gas attack that killed hundreds of civilians, Interior Minister Manuel Valls said.

Valls made the comments on Sunday to Europe 1 radio as pressure mounted in France for President Francois Hollande to put the question of intervention to a parliamentary vote.

Also on Sunday, Prime Minister Jean-Marc Ayrault said he would meet with the heads of the two houses of parliament and the opposition on Monday to discuss Syria before a scheduled parliamentary debate on Syria on Wednesday.

"France can not go it alone," Valls said. "We need a coalition."

Valls said the announcement by President Barack Obama on Saturday that he would seek authorization from lawmakers before any strike created "a new situation" which meant France would have to wait "for the end of this new phase."

On Friday, Hollande said a British parliamentary vote against military action in Syria would not affect France's will to punish Assad's government, which it blamed for the gas attack.

A BVA poll on Saturday showed most French people do not approve of military action against Syria and most do not trust Hollande to conduct such an operation.

In an unexpectedly assertive move, Hollande, whose popularity has been hurt by economic gloom, sent troops this year to help Mali's government fend off Islamist rebels, an intervention backed by two-thirds of the public.