U.S. President Donald Trump speaks to reporters before leaving the White House in Washington D.C., the United States, on Dec. 2, 2019. U.S. President Donald Trump slammed an ongoing impeachment inquiry into him on Monday, as the next phase of the high-stake investigation was drawing near. (Photo by Ting Shen/Xinhua)

US President Donald Trump launched a two-day NATO meeting Tuesday with a blistering attack on France's criticism of the alliance and on "delinquent" members that don't pay their way.

At a news conference held to celebrate NATO's success in cajoling European allies to boost their defense spending, Trump could not resist lashing out at French President Emmanuel Macron.

Macron had tried to shake up the agenda for the London summit by branding the 70-year-old Western alliance "brain-dead," but Trump slapped him down and warned that he could see Paris "breaking away" from NATO.

"NATO serves a great purpose," Trump said, at a joint press appearance with alliance Secretary-General Jens Stoltenberg.

"I think that's very insulting," he said of Macron's comment, branding it a "very, very nasty statement essentially to 28 countries.

"Nobody needs NATO more than France," he said. "It's a very dangerous statement for them to make." 

Asked whether the US alliance with NATO was shaky, Trump denied it, but said, "I do see France breaking off... I see him breaking off."

If the Macron comments set an angry tone for the meeting, there are also expected to be clashes with Turkey's President Recep Tayyip Erdogan, who was also furious with the French leader.

"First of all, have your own brain death checked. These statements are suitable only to people like you who are in a state of brain death," he said last week.

French officials summoned the Turkish envoy in Paris to complain while a US administration official predicted that many members would tackle Turkey over its purchase of a Russian S-400 air defense system.

Turkey, in turn, has warned it will block a NATO plan to defend Baltic countries unless the alliance recognizes a Kurdish militant group as terrorists, Erdogan said before the summit.

It was reported last week that Ankara was blocking NATO's new Baltic defense plan, demanding greater support in its fight against the Syrian Kurdish People's Protection Units.

NATO has mooted a plan to bolster the defenses of Poland, Estonia, Lithuania and Latvia against a potential attack from Russia, though details remain unclear.