Donald Trump announced that Nato members will significantly increase their military spending, after he apparently threatened to pull the US out.
In an impromptu press conference this morning, Trump said he had "told people he would be very unhappy if they did not up their commitments very substantially".
He claimed the combined additional sum would be $33bn, but said that could rise to $40bn, with other economies agreeing to meet Nato's target of two per cent of GDP. Trump said that would happen over "a fairly short period of time".
"We are paying far too much for Nato," he said. "Nato is very important but it's helping Europe far more than it's helping us."
Asked if he threatened to leave, Trump did not give a direct answer.
"I told them I would be very unhappy if they did not up their commitments substantially. I let them know I was extremely unhappy with what was happening and now they have upped their commitment, and now... we have a very strong Nato," he said.
"They were probably worried," he added, saying he was "very firm".
The US President told allies that unless the wealthiest economies in the North Atlantic Treaty Organisation - Germany, France, Spain and Italy for example - hit their two per cent target by January "we are going to do our own thing”, The Times reported.
Asked about his trip to the UK, Trump said he was not concerned about protests because "they like me a lot there", suggesting the Brexit vote had come about because "they agree with me on immigration".
But he noted he was "going to a pretty hot spot, with a lot of resignations right now".
He added: "I’ve been reading a lot about Brexit over the last couple of days and it seems to be turning a little bit differently, where they’re getting at least partially involved back with the European Union."
He stressed it was not for him to say, despite owning "a lot of property there" and the fact his mother was born in Scotland.
Trump added: "I'd like to see them work it out quickly... Is it heartbreaking? That might be going a little bit far. I would say Brexit is Brexit. The people voted to break it up so I imagine that's what they'll do but maybe they'll take it in a little bit of a different route. I dont know if that's what they voted for... I just want the people to be happy."
Separately, Trump also dealt with the ongoing discussions with the EU on the steel and aluminium tariffs, noting that "Both of my parents are from the EU, despite the fact they don't treat us well on trade".
He added: "If the EU do not offer the US a better deal on trade, the US will do something about European cars being imported at a very low tariff."