The French president was not amused. “Let's be serious,” Macron implored Trump, asserting that “foreign fighters coming from Europe” represent only a “tiny minority of the overall problem” posed by radical militants in the region.

“I think, No. 1 priority, because it's not yet finished, is to get rid of ISIS and these terrorist groups. This is our number one priority. And it's not yet done, I'm sorry to say that,” he said.

Macron also lamented the “destabilization” of the Middle East which has made efforts to counter the ISIS threat “more difficult” — an oblique criticism of Trump’s tacit approval of a Turkish incursion into northern Syria and subsequent directive to withdraw the last U.S. troops from the area.

“This is why he's a great politician,” Trump retorted. “Because that was one of the greatest non-answers I've ever heard, and that's OK.”

The president later conceded that France “has actually taken back some fighters,” insisted that “100 percent” of the ISIS caliphate had been captured, touted the American forces remaining on the ground in Syria to defend its lucrative oil fields, and boasted about the special operations raid that resulted in the death of ISIS leader Abu Bakr al-Baghdadi.

“A lot of things are happening, and France has been very helpful, I have to say that. They've been very, very helpful,” Trump said.

His on-camera collision with Macron marked what could be the first of many testy exchanges between Trump and fellow leaders this week regarding the administration's jarring series of policy shifts in Syria two months ago, which were met with sustained criticism from congressional lawmakers and the international community.

Trump's decision to allow Turkey's military to invade resulted in the slaughter of the U.S.-allied Kurdish soldiers and the escape of dozens of ISIS fighters, and ultimately paved the way for geopolitical foes including Russian President Vladimir Putin and Syrian President Bashar Assad to exert greater regional influence.

In a more direct rebuke of the president's diplomacy Tuesday, Macron acknowledged Trump's concerns about equitable defense spending among NATO members, but also warned of the dire threats facing the military alliance.

“When I look at Turkey, they now are fighting against those who fight with us — who fought with us shoulder-to-shoulder against ISIS. And sometimes they work with ISIS proxies,” he said. “This is an issue, and this is a strategy issue. If we just have discussion about what we pay, and we don't have clear discussions about the situation, we are not serious. We are not serious for our soldiers. We are not serious for our people.”