Speaking to reporters in the Oval Office, Mr Trump said: "When I came to Nato, when I first had my first meeting, I noticed that people weren't paying their bills at all, and I said I should wait till my second meeting.

"And I did. And I brought that up, and I said, 'if you don't pay your bills, we're not going to participate. We're not going to protect you'.

"And when I said that, as soon as they said that, it was amazing how the money came in, the money came in, and now they have money. But even now, it's not enough. They should be paying more."

His comments come after it was reported the administration is redrawing Nato engagement in a way that favours member countries with higher defence spending.

The president is also said to be considering prioritising military exercise with member countries that are spending the set percentage of GDPs on their defence, officials told the broadcaster.

Mr Trump has repeatedly criticised Nato countries for not meeting the current two per cent spending goal, arguing that the disparity puts an unfair burden on the United States which spends around 3.4 per cent of its GDP on defence, according to the Stockholm International Peace Research Institute ( SIPRI ).

"Nato has to pay more," Mr Trump said in January after taking office. "It's ridiculous because it affects them a lot more. We have an ocean in between."

The move would come after Sir Keir Starmer announced that he would meet a commitment to spend 2.5 per cent on defence by 2027, an investment he hoped would improve his relationship with the president.

In what he called the "biggest sustained increase in defence spending since the end of the Cold War," Sir Keir said the increase will be funded by a cut to the overseas aid budget, which will be reduced from 0.5 per cent of GDP to 0.3 per cent.

Poland has the highest dedicating 4.12 per cent of its GDP to the cause.

"He wants to rework it so it is more favourable to those that spend more," a source close to the administration told The Telegraph.

"He is saying to European leaders that beating your chest and cashing the cheque are two different things."

Facing the prospect that the United States might cut them adrift under Mr Trump, European Union leaders launched a day of emergency talks on Thursday in an attempt to beef up their own security and ensure Ukraine will still be protected.