WASHINGTON - US President Donald Trump once again questioned the role of the North Atlantic Treaty Organization (NATO), casting doubt on whether other members of the military alliance would defend America if it were attacked.

"You know the biggest problem I have with NATO? ... I know the guys very well. They're friends of mine. But if the United States was in trouble, and we called them ... Do you think they're going to come and protect us? They're supposed to. I'm not so sure," Trump said Thursday in the Oval Office.

French President Emmanuel Macron responded to Trump's remarks by telling reporters at a European Union summit Thursday in Brussels that France and the United States have "always been there for each other" throughout history.

France had shown "respect and friendship" toward the United States, Macron said. "I think we're entitled to expect the same."

The French leader also mentioned that NATO members joined the US-led war in Afghanistan after the 9/11 terror attacks.

That has been the first and only invocation to date of Article 5 of the North Atlantic Treaty, known as collective defense.

"Not only the French, but the Europeans were there when we were called for Afghanistan. And by the way, they weren't politely warned when (the US left Afghanistan)," Macron said. "We are loyal and faithful allies."

Trump, who has criticized other NATO members for not spending enough on defense, is considering a major change to Washington's engagement with NATO, NBC News reported.

As part of the potential policy shift, the United States might not defend a fellow NATO member that is attacked if the country does not meet a certain defense spending threshold set by Washington, it said, citing anonymous officials.

Should the policy change be implemented, it would mark a significant shift away from Article 5, which says an attack on any NATO country is an attack on all of them.

In addition, the United States may also prioritize military exercises with NATO members that are spending a set percentage of their GDP on defense, according to the report.