Donald Trump's grasp of Nato was questioned on Sunday after he claimed that Germany owed the Western alliance and the United States "vast sums of money"
The president had demanded in a tweet on Saturday that "the United States must be paid more for the powerful, and very expensive, defense it provides to Germany!"
Despite what you have heard from the FAKE NEWS, I had a GREAT meeting with German Chancellor Angela Merkel. Nevertheless, Germany owes.....— Donald J. Trump (@realDonaldTrump) March 18, 2017
...vast sums of money to NATO & the United States must be paid more for the powerful, and very expensive, defense it provides to Germany!— Donald J. Trump (@realDonaldTrump) March 18, 2017
But his demand was swiftly rejected by German Defence Minister Ursula von der Leyen, who said on Sunday that "there is no debt account at Nato."
She added: "Defence spending also goes into UN peacekeeping missions, into our European missions and into our contribution to the fight against IS terrorism."
Nato - which stands for North Atlantic Treaty Organisation - is an alliance of western countries, including the UK, which have agreed to defend each other against an attack from an external threat, such as Russia.
Ivo Daalder, the former US ambassador to Nato, also took issue with Mr Trump's claims and replied directly to the president on Twitter.
"I'm sorry, Mr President but that is not how Nato works," he said, pointing out that Nato spending was not a "financial transaction" between countries but a joint commitment to spend two per cent of GDP on defence.
1/ Sorry, Mr. President, that’s not how NATO works. The US decides for itself how much it contributes to defending NATO. pic.twitter.com/8svkzRBEQb— Ivo Daalder (@IvoHDaalder) March 18, 2017
4/ Those who currently don’t spend 2% of their GDP on defense are now increasing their defense budgets. That’s a good thing.— Ivo Daalder (@IvoHDaalder) March 18, 2017
He went on to argue that America's large military commitment to Nato was not a "favour to Europe" but a mutually beneficial arrangement as keeping Europe "whole and free" was key to US interests.
Mr Trump has clashed with Germany in the past as it currently spends just 1.18 per cent of GDP on defence, according to the latest figures.
But Angela Merkel, the German chancellor, reiterated Germany's intention to increase spending to two per cent during a press conference with Mr Trump on
The president's stance on Nato appears to have softened slightly since the election campaign, when he rejected the military alliance as "obsolete."