In a short statement on Wednesday, NATO endorsed a higher defence spending goal of five per cent of GDP by 2035 - a response to a demand by Trump and to Europeans' fears that Russia poses a growing threat to their security following the 2022 invasion of Ukraine.
"We reaffirm our ironclad commitment to collective defence as enshrined in Article 5 of the Washington Treaty - that an attack on one is an attack on all," the statement said, after Trump had sparked concern on Tuesday by saying there were "numerous definitions" of the clause.
But just before the summit opened, Trump had said of fellow NATO members: "We're with them all the way."
The 32-nation alliance for its part heeded a call by Trump for other countries to step up their spending on defence to reduce NATO's reliance on the US.
NATO Secretary-General Mark Rutte acknowledged that it was not easy for European countries and Canada to find the extra money, but said it was vital to do so.Â
"There is absolute conviction with my colleagues at the table that, given this threat from the Russians, given the international security situation, there is no alternative," the former Dutch prime minister told reporters in his home city of The Hague.
The new spending target - to be achieved over the next 10 years - is a jump worth hundreds of billions of dollars a year from the current goal of two per cent of GDP, although it will be measured differently.
Countries would spend 3.5 per cent of GDP on core defence - such as troops and weapons - and 1.5 per cent on broader defence-related measures such as cybersecurity, protecting pipelines and adapting roads and bridges to handle heavy military vehicles.
All NATO members have backed a statement enshrining the target, although Spain declared it does not need to meet the goal and can meet its commitments by spending much less.
Rutte disputes that but accepted a diplomatic fudge with Spanish Prime Minister Pedro Sanchez as part of his efforts to give Trump a diplomatic victory and make the summit go smoothly.
Spain said on Wednesday that it did not expect its stance to have any repercussions.
Rutte has kept the summit and its final statement short and focused on the spending pledge to try to avert any friction with Trump.
Ukrainian President Volodymyr Zelenskiy had to settle for attending the pre-summit dinner on Tuesday evening rather than the main meeting on Wednesday, although he was set to meet Trump separately.
Hungarian Prime Minister Viktor Orban diluted the display of unity when he told reporters that NATO had no business in Ukraine and that Russia was not strong enough to represent a real threat to NATO.
The Kremlin has accused NATO of being on a path of rampant militarisation and portraying Russia as a "fiend of hell" in order to justify its big increase in defence spending.
