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.
By pointing out the close connections between Germany and Russian Federation on the Nord Stream 2 gas pipeline, and the degree to which they depend on each other financially, Trump was borrowing a page from his critics who suggest that because of Russia's interference in the 2016 election on his behalf, he is beholden to Putin.
It would also include "the activities of each such allied nation to contribute to military or stability operations in which the Armed Forces of the United States are a participant; any limitations placed by any such allied nation on the use of such contributions; and any actions undertaken by the United States or by other countries to minimize such limitations".
With that, Trump moved on to the United Kingdom, where significant protests against him were expected.
Instead, a series of events - a black-tie dinner with business leaders, a meeting with Prime Minister Theresa May and an audience with Queen Elizabeth II - will happen outside the bustling city, where Mayor Sadiq Khan has been in a verbal battle with Trump.
Newly-discovered fossils suggest giant dinosaurs evolved earlier
The last, iconic sauropods had the benefit of a long history of evolutionary innovation in this regard, said Dr Apaldetti. We have seen dinosaurs only on the big screens or theme parks and they seem intriguing creatures.
"I think we will be able to", he said. "I mean, I think they like me a lot in the United Kingdom, I think they agree with me on immigration".
"I just came from the region and people are genuinely concerned about how reliable we are as a partner", said retiring Foreign Relations Chairman Bob Corker of Tennessee. That would mark a significant milestone for the alliance.
"The commitment was at two percent and that'll be going up quite a bit higher than that", he said. The target date to get military spending to 2% is 2024. Officials said no explicit threat was made.
"I told people that I would be very unhappy if they didn't up their commitments", an ebullient president told reporters after the second day of the Brussels meeting, when North Atlantic Treaty Organisation leaders huddled with Trump to try to defuse a crisis.
While in Latvia earlier this week, when asked about plans to meet the target, the prime minister made it clear he had no plans to double Canada's defence budget.
As well as Merkel, Spanish Prime Minister Pedro Sanchez and Charles Michel, the prime minister of Belgium, were singled out by Trump for undershooting on their spending targets when USA taxpayers, funding a defence budget worth about 3.6 percent of their national income, foot much of NATO's bills.
North Korean officials no-show for meeting about US troop remains
Both sides were expected to discuss the timeline and ways in which remains of American soldiers would be returned at the meeting. However, officials say it could be months before excavations can begin and years until the remains are identified.
French president Emmanuel Macron indicated there was no commitment beyond current pledge to spend 2 per cent of GDP.
Trump took his war of words with America's allies to a new level Wednesday, telling NATO's top official that Germany is "captive" to Russian Federation due to a recent energy deal.
The president has been highly critical of the alliance, complaining the United States pays more than others.
"The fact is that we have a commitment to increase defense spending".
Shelby pointed to the importance of Trump being properly briefed ahead of the sit-downs.
Is this what the US President really thinks of London?
London Mayor Sadiq Khan approved the blimp earlier this week, ahead of Trump's visit to the city. The US president will touch down at Stansted Airport on Thursday evening.