The French leader has said that Paris could launch unilateral air strikes against targets in Syria if a new chemical attack took place.

:: President Emmanuel Macron agreed with US President Donald Trump in a phone call on Tuesday that they would work together to find a common response in case of a new chemical attack in Syria, the French presidency said in a statement.

The United States had earlier warned Syria’s leadership against staging a chemical weapons attack after Washington detected what appeared to be active preparations at a Syrian airfield used for such an attack in April, US officials said on Tuesday.

“They discussed the Syria dossier and the necessity to work on a common response in case of a chemical attack,” Macron’s office said in a statement.

It gave no further details.

The US had recently seen activity at Shayrat airfield, the same base targeted by a unilateral US cruise missile strike on April 6, officials said.

The French leader has said that Paris could launch unilateral air strikes against targets in Syria if a new chemical attack took place.

French diplomats and defense officials said that there had been no specific information passed on to Paris on the new activity.

“It seems to be a message to the Russians,” said one official. “That suits us and fits into Macron’s red line on the use of chemical weapons.”

The French presidency declined to comment.

Macron appears to be broadly aligning his foreign policy with the US priorities of tackling terrorism while seeking better ties with Russia, which he considers a long-term partner rather than a direct threat to Europe.

Macron also invited Trump to attend the July 14 Bastille Day celebrations in Paris, which will this year, commemorate 100 years since the United States entered World War One.