Mr Trump's early-morning tweets from Brussels had been typically critical.
Trump called those commitments a major victory; they were first made in 2014.
Trump's demand jolted the transatlantic alliance at the conclusion of this week's Brussels summit and, in the words of one diplomat briefed on the events, sent "everyone into a tailspin". But at the bilateral meeting he exulted: "We have a very, very good relationship with the Chancellor".
After a tense first day, Trump didn't ease up on the second.
"German foreign minister lashed out at the U.S. President Donald Trump's criticism over Russia's sale of liquefied natural gas to Berlin, saying "we are not captives" of Russian Federation or the U.S". But not before Merkel and other top officials in the German government had publicly fired back at Trump's breakfast diatribe.
"We are doing numbers like they've never done before or ever seen before", Trump said. There was a great collegial spirit in that room. "He does not see the value, and does not recognize that the U.S. also benefits from it". Trump has repeatedly denounced low levels of defense spending among remaining members, particularly Germany. Allies would be increasing spending by $33 billion or more, he added.
The size of a nation's particular GDP is irrelevant, she argued, and warned Europe that following the wasteful habits that Trump has embraced in the US could be a recipe for disaster.
Breaking from a carefully scripted session that was to focus on Ukraine and Georgia, one source said Trump "forcibly restated his position on wanting North Atlantic Treaty Organisation members to reach 2 percent spending target to a short a deadline".
Trump has several times assailed Germany for not spending a large enough proportion of its gross domestic product on defense. "There is a communique that was published yesterday". Very unified, very strong.
He added: "It confirms the goal of 2 percent by 2024".
"As we engage Russian Federation we must do so from a position of unity and strength - holding out hope for a better future, but also clear and unwavering on where Russian Federation needs to change its behavior for this to become a reality, " she said. "The additional money they will be putting up has been really fantastic".
Praising new initiatives to build capacity, NATO Secretary General Stoltenberg estimated that as much as 266 billion additional US dollars would be spent by European allies and Canada on defense by 2024.
What NATO partners dispute is Trump's repeated suggestion that the US gets little in return for its commitment to defend member countries if threatened. But Nato sources, speaking to Reuters, said he had denied making such a threat. "I'm a very stable genius".
Trump is scheduled to meet with Putin on Monday in Helsinki, Finland.
"Will they reimburse the US?"
It's an uncomfortable environment for May, who is facing her own political unrest outside of Trump's visit.
The mood was already prickly ahead of the summit, prompting a terse exhortation from the European Union's President Donald Tusk for Trump to "appreciate" his allies and reminding him that Europe had come to its aid following the 9/11 attacks. He described the U.K.as a "hot-spot with lots of resignations". The officials said Trump threatened to "do his own thing".