The US President did not hold back as he addressed fellow Nato members and insisted “the NATO of the future must have a great focus on terrorism and immigration”.
He said: “I have been very very direct… in saying that Nato members must finally contribute their fair share and meet their financial obligations.
“But 23 of the 28 member nations are still not paying what they should be paying and what they’re supposed to be paying for their defence.”
Donald Trump speaking ahead of Nato summit
He said Nato’s reliance on America money was “unfair” as the EU leaders looked at each other in shock during the address.
Mr Trump continued: “This is not fair to the people and taxpayers of the United States and many of these nations owe massive amounts of money from past years and not paying in."
“Those paying in the past years over the last 8 years the United states spent more on defence than all other Nato countries combined if all Nato members had spent just 2 per cent of their GDP on defence last year, we would have had another ¢199bn for our collective defence.
Nato members are expected to spend two per cent of GDP on their military budget, as the alliance looks to bolster its global presence.
President Trump has previously ripped into members for failing to meet the criteria and said he would not allow the USA to shoulder their burden.
The American is expected to hold "very tough" talks as he meets with Nato military leaders in Brussels.
Nato chiefs have already agreed to his request to join the US-led coalition against ISIS in Iraq and Syria.
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President Trump also met with EU leaders to discuss Nato
Last November, it was reported only the US, Greece, United Kingdom, Estonia and Poland were contributing the agreed two per cent target.
Some of Europe's biggest economies, Germany and France, failed to offer up enough military spending, which angered the US President.
Nato leaders are likely to see President Trump's meeting as a positive step, with the American previously labelling the alliance "obsolete".
He has since, however, taken a U-turn on the statement and showed his support for Nato.
He spoke about the unveiling of a piece of the North Tower from the 9/11 attacks and a part of the Berlin Wall, which has gone on display at the new building.
The American then cracked a joke that he has never "once" had to ask how much the new headquarters had cost to build, while Nato members continue to fail to reach spending commitments.
Donald Trump said: "I want to extend my appreciation to the 9/11 Memorial and Museum in New York for contributing this remnant of the North Tower, as well as to Chancellor Merkel and the German people for donating this portion of the Berlin Wall.
"It's truly fitting that these two artefacts now reside here so close together at the new Nato headquarters."
The President then quipped: And I never once asked what the new Nato headquarters cost – I refuse to do that."
NATO countries' heads of states gather in Brussels
Thu, May 25, 2017
NATO countries' heads of states and governments gather in Brussels for a one-day meeting
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A family picture during the NATO (North Atlantic Treaty Organization) summit at the NATO headquarters, in Brussels, on May 25, 2017
Prime Minister Theresa May is also keen to meet with the President while he is in Europe for the Nato summit.
On Thursday, Mrs May said she would tell President Trump that intelligence shared between their two countries must remain secure after leaks to US media about the Manchester bombing.
Mrs May said she would talk to the American about the leaks, which included the publication of photographs of the bomb site by the New York Times.