Donald Trump speaks during his meeting with NATO Secretary General, Jens Stoltenberg in London. Evan Vucci/AP

US President Donald Trump launched an angry broadside against his European allies ahead of a NATO summit in London on Tuesday, singling out France's Emmanuel Macron for "very nasty" comments on the alliance and Germany's shortfall on funding commitments.

Underlining the breadth of strife in a transatlantic bloc hailed by its backers as the most successful military alliance in history, Trump demanded that Europe pay more for defence and also make concessions to US interests on trade.

US President Donald Trump (right) grimaces during a meeting with NATO Secretary General, Jens Stoltenberg in London. AP

The attack echoed a similar volley of abuse by Trump ahead of NATO's July 2018 summit. It will add to the growing doubts over the future of the bloc, described by Macron as "brain dead" in the run-up to a London meeting intended to be a 70th anniversary celebration.

"It's a tough statement, though, when you make a statement like that, that is a very, very nasty statement to essentially 28, including them, 28 countries," Trump told reporters as he met the head of NATO in London.

Explicitly linking his complaint that Europe does not pay enough for NATO's security missions to his staunch "America First" defence of US commercial interests, Trump said it was time for Europe to "shape up" on both fronts.

"It's not right to be taken advantage of on NATO and also then to be taken advantage of on trade, and that's what happens. We can't let that happen," he said of transatlantic disputes over everything from the aerospace sector to a European "digital tax" on US technology giants.

Dismissing recent signals from Germany that it was ready to do more to match a NATO target of spending two percent of national output on defence, Trump accused it and other nations which spend less than that target of being "delinquent".

Reuters