France's foreign minister said on Tuesday there were signs that chemicals had been used in attacks by Syrian government forces on rebels in northwest Syria, but they still needed to be verified.
The United States said on May 23 it had received numerous reports that appeared consistent with chemical exposure after forces loyal to Syrian President Bashar al-Assad launched an offensive on the rebel stronghold.
"We have a sign of the use of chemical weapons in the Idlib area but for now there isn't verification," Jean-Yves Le Drian told the French parliament's foreign affairs committee.
"We are cautious because we think that the use of chemical weapons must be confirmed and lethal before we react," he said.
Syria's government denies using chemical weapons.