President Donald Trump spent his first hours at the NATO summitpublicly bashingthe alliance and reciting a list of grievances that had allies fearing the worst.

Then he went behind closed doors and changed his tune.

The president was far more positive on Wednesday, when he gave a final 30-minute speech which left out his desire to annex Greenlandor criticize Spain, his latest European punching bag, according to four people, who were granted anonymity to relay details of the private meeting. While there was some criticism, there were also plenty of compliments.

"We want to remain with you," Trump said, according to a second participant in the meeting.

The shift was a notable about-face for a president who has threatened repeatedly to leave the alliance — and came after European leaders heaped praise on Trump for helping ensure allies boosted their defense spending. But those in attendance weren't clear what specifically changed his stance.

"It was a bit unexpected, the mood in the room was a lot better than it seemed before," according to one of the four people. "His mood seems to have swung."

Trump bragged about the U.S. military's prowess and thanked leaders from Poland, Germany, the Baltic states and Norway for their contributions to the alliance.

"We just had our NATO meeting, and it was a great meeting," Trump said ahead of a separate meeting with Ukrainian President Volodymyr Zelenskyy. "You probably heard it was a great meeting, a lot of…there was a lot of love in that room."

His remarks represented a sharp turn from his condemnations on Tuesday and Wednesday when he lambasted NATO for failing to help with the Iran war and bristled at Spain's refusal to spend more on defense. Trump went so far as to call for the U.S. and other countries to cut ties with Spain.

He didn't mention any particular nations on the "naughty list" in the meeting, said one diplomat. "Just in his public remarks."

The turnaround also underscores why European leaders remain on tenterhooks around the president, who relishes his own unpredictability. America's carefully crafted diplomatic statements are increasingly a relic and what Trump says at one meeting may not represent his views at the next.

"I mean that's what's in the room," said an alliance official, granted anonymity to speak candidly. "Let's see what he says in public."

European leaders have gone out of their way to praise the U.S. president during the summit. NATO chief Mark Rutte even told POLITICO that Trump's push to boost defense spending is "great news" for allies.

But the tension is far from settled. Hanging over the remainder of the conference is the renewed hostilities with Iran and the issue of Greenland, which Trump has insisted needs to be "controlled" by the U.S.

Shortly after Trump's earlier bombastic remarks about Greenland, Danish Prime Minister Mette Frederiksen said the island was not for sale, a position shared by her alliance colleagues.

"It is a well-known position of the United States that it wants to own and take over Greenland," Frederiksen said. "I hope that it is equally well-known everywhere that this is not going to happen."