After President Trump warned Syria’s Bashar al-Assad of a “big price to pay” following an apparent chemical attack April 7, he received support from a continent that has so far been mostly wary of his policies. French President Emmanuel Macron and Trump discussed the Syrian attack in a phone call Sunday and subsequently vowed a “strong, joint response,” according to a White House statement.

France and the United States were continuing to coordinate a possible response Monday, as Syria and Russia both claimed that Israeli warplanes had carried out a missile strike on an air base in central Syria hours earlier. Israel did not immediately comment, and the Pentagon said it had not conducted any strikes in the region.

But the lack of a U.S. response is probably only temporary. Despite the cracks in transatlantic relations that have emerged in recent months, France’s Macron might this time be keen on having the United States on his side — and vice versa.

Like President Barack Obama in 2012, Macron has declared the use of chemical weapons by the Syrian regime a “red line” and has repeatedly pledged to strike any chemical weapons sites in Syria connected to attacks.

The question is whether Macron — unlike Obama — will follow through. Teaming up with Trump, who has frequently lashed out at his predecessor for failing to rein in the Assad regime, could make it easier for Macron to defend sticking to his pledge.

“Especially with Macron's state visit to Washington coming up,  I don’t think that Macron would do anything that’s not coordinated with the White House,” said Nicholas Dungan, a France-based senior fellow with the Atlantic Council. “If necessary, France would be willing to act alone, but it wouldn’t act in isolation. If they opted for military action, the French would expect the support of the other major NATO allies.”

Still, France’s approach has so far been much more cautious than Washington’s responses to any apparent use of chemical weapons.

A statement released Sunday by the French government indicated the United States and France were still working on gathering evidence on the details of the attack. Those efforts will probably also be discussed in the U.N. Security Council on Monday, and the two leaders are scheduled to discuss a response by Tuesday, at the latest.

France’s statement following the Sunday call appeared to be a toned-down version of a White House statement. While the White House specified “both leaders strongly condemned the horrific chemical weapons attacks in Syria and agreed that the Assad regime must be held accountable for its continued human rights abuses,” the French remarks appeared to echo previous comments by Macron in which he emphasized that he would take action only if there was specific evidence.

“If we have proven evidence that chemical weapons proscribed in treaties are used, we will strike the place where they are made,” Macron said in February, before cautioning: “Today, our agencies, our armed forces have not established that chemical weapons, as set out in treaties, have been used against the civilian population.” In a March news conference, Macron made the existence of “irrefutable evidence” the condition for any military strikes and explained that close coordination with the United States may not necessarily lead to joint strikes or action.

“The day we have, in particular in tandem with our American partners, irrefutable proof that the red line was crossed — namely the chemical weapons were used to lethal effect — we will do what the Americans themselves did a few months ago; we would put ourselves in position to proceed with targeted strikes,” Macron said back in March. The president was referring to the 2017 strikes, ordered by Trump in response to the Khan Sheikhoun chemical attack that occurred days earlier, when 59 U.S. Tomahawk cruise missiles targeted Syria’s Shayrat air base in response.

Syria has denied using chemical weapons against civilians — including in Khan Sheikhoun — but Syria observers are accusing the regime of covering up its attacks.

Supporters of more decisive military action against the Syrian regime have criticized Macron for stepping up his rhetoric in recent months but not taking any action. The French leader has also avoided specifying whether the use of chlorine gas in an attack would be categorized as a chemical weapons attack, even though the Arms Control Association and other organizations classify chlorine as a potential chemical agent.

Macron now appears to have three core options on Syria. He could refrain from any action, citing a lack of evidence but risking the loss of credibility Obama faced after he refrained from reining in Syria. Alternatively, he could team up with Trump and strike Syrian targets — and risk being drawn into the conflict. Less likely is that France would have to launch a strike without U.S. support, given that Washington has so far appeared willing to blame the Syrian regime for chemical attacks even as other nations said the existing evidence was too thin.

It remains in doubt whether strikes could significantly damage Syrian military infrastructure or prevent future chemical attacks. Even though Syrian outlets described the impact of the 2017 U.S. strikes on Shayrat air base as severe, there were also reports that it was back in use days later.

“The problem here is not a possible military response to an incident, but rather a long-term policy as to what it is the West wants to achieve in order to end the Syrian civil war,” said France-based researcher Dungan. Joint military strikes, he said, would do little to address that broader question.

But to Macron, perhaps the more important question right now is whether he is okay with becoming the next world leader to draw a “red line,” only to subsequently ignore it and open himself up to mockery.

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