Then, in a head-snapping pivot at the end, on Thursday he declared the alliance a "fine-tuned machine" that had acceded to his demands to speed up increases in military spending.
Trump has vented over the lack of progress in Afghanistan, other officials say.
"Trump arrived 30 minutes late to today's North Atlantic Treaty Organisation summit, missed his scheduled meetings with at least two world leaders, prompted the secretary general to call an emergency session, held an impromptu 35-minute news conference, and is now leaving for the airport go fly to London", tweeted Rebecca Ballhaus, a Wall Street Journal reporter covering the summit from Belgium.
Trump said he and Merkel also talked about the pipeline project that he railed about during a breakfast meeting with NATO Secretary-General Jens Stoltenberg, but would not comment on what they discussed.More news: HP Chromebook x2 variant sounds like the Surface Go
Trump claimed member nations had agreed to significantly boost their defence budgets and reaffirmed - after days of griping that the USA was being taken advantage of by its allies - that the US remains faithful to the accord.
"Our President - the orange guy Trump- is in Belgium right now - at the NATO Summit, fighting over how many ways they will split the check", Jimmy Kimmel told his late night viewers about POTUS's latest. But I said, ultimately we should be - in years in advance, we should be at 4 percent.
The United States, far the biggest economy, spent 3.6 percent past year, while Germany, the second biggest, paid out just 1.2 percent and only a handful of countries met the 2 percent target. "The alliance can rely on the U.K.to lead by example". Flake questioned why the two were meeting without staff, noting that the "world seems to be hanging in the balance". "I'm very strong on immigration". Allies will deliver on fairer burden-sharing, he said, pointing out that European Allies and Canada are expected to spend an extra $266 billion on defence between now and 2024.
According to diplomats, he plunged the summit into chaos on Thursday by saying that the USA would "go it alone", if European states failed to boost their spending to at least 2% by January.More news: Russian cargo ship docks at ISS in record time
Leaving Nato would be a seismic step, previously unthinkable, that would shake up a western alliance that has endured for more than 70 years.
"President Trump never at any moment, either in public or in private, threatened to withdraw from NATO", Macron said. "It confirms the goal of 2 percent by 2024".
Under fire for his warm embrace of Russia's Vladimir Putin, Trump on Wednesday also turned a harsh spotlight on Germany's own ties to Russian Federation, alleging that a natural gas pipeline venture with Moscow has left Angela Merkel's government "totally controlled" and "captive" to Russian Federation.
"And frankly maybe everyone is going to have a good relationship with Russian Federation".More news: India adopts 'world's strongest' net neutrality norms
Trump would normally first need to win approval in the Senate and to persuade Republican senators that the move was necessary and in the US's long-term security interests.
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