US President Donald Trump has suggested that Nato allies double their defence spending targets, as member countries struggle to meet their current funding goals.

Mr Trump told attendees at the Nato summit in Brussels this week that every member nation should be spending 4 per cent of their GDP on defence annually.

“President Trump wants to see our allies share more of the burden and at a very minimum meet their already stated obligations,” White House press secretary Sarah Huckabee Sanders said in a statement.

Mr Trump falsely claimed earlier this week that the US already spends 4 per cent of its GDP on defence. According to Nato, the US spent 3.57 per cent of its GDP on defence last year, and is projected to spend 3.5 per cent this year.

Mr Trump has long complained that other 28 Nato member countries do not contribute enough money towards their own defence, claiming the US is footing the bill for their protection. He previously raised the issue of increased spending targets with Nato Secretary General Jens Stoltenberg when he visited the White House last year.

Nato leaders gather for summit: in pictures Show all 10 1 /10 Nato leaders gather for summit: in pictures Nato leaders gather for summit: in pictures World leaders gather for Nato family photo Getty Images Nato leaders gather for summit: in pictures British Prime Minister Theresa May arrives EPA Nato leaders gather for summit: in pictures President Donald Trump talks to British Prime Minister Theresa May EPA Nato leaders gather for summit: in pictures U.S. President Donald Trump, left, talks to British Prime Minister Theresa May during a family photo at a summit of heads of state and government at NATO headquarters in Brussels Wednesday, July 11, 2018. NATO leaders gather in Brussels for a two-day summit to discuss Russia, Iraq and their mission in Afghanistan. (AP Photo/Markus Schreiber) Markus Schreiber AP Nato leaders gather for summit: in pictures US President Donald Trump and Nato Secretary General Jens Stoltenberg attend a bilateral breakfast ahead of the Nato Summit in Brussels Reuters Nato leaders gather for summit: in pictures President Donald Trump, right, gestures as he speaks to the media prior to his bilateral breakfast with Nato Secretary General Jens Stoltenberg, left AP Nato leaders gather for summit: in pictures President Donald Trump, US Secretary of Defence James Mattis and US Secretary of State Mike Pompeo at the bilateral breakfast with Nato Secretary General Jens Stoltenberg REUTERS Nato leaders gather for summit: in pictures President Donald Trump and Mike Pompeo, left, are reflected in a mirror as they attend at a breakfast meeting AFP/Getty Images Nato leaders gather for summit: in pictures President Donald Trump speaks during the bilateral breakfast EPA Nato leaders gather for summit: in pictures President Donald Trump gestures during the bilateral breakfast EPA

Mr Stoltenberg said on Wednesday that the member countries were working towards a goal of spending 2 per cent of their respective GDPs on defence – a number agreed upon at a 2014 summit in Wales.

The announcement appeared not to impress Mr Trump, who tweeted: "Why are there only 5 out of 29 countries that have met their commitment? The US is paying for Europe’s protection, then loses billions on Trade. Must pay 2% of GDP IMMEDIATELY, not by 2025.”

Mr Trump reportedly sent letters to several Nato member countries ahead of the summit, accusing them of underspending on their defence and warning that the current situation was “no longer sustainable” for the US.

Donald Trump says Germany 'totally controlled' by Russia

The summit itself has started on a tense note, with Mr Trump tearing into Germany during a breakfast meeting. The president accused Germany of skimping on its defence payments while giving “billions and billions of dollars a year to Russia” – a situation he called “very inappropriate”.

German Chancellor Angela Merkel shot back, noting that Germany is the the second largest donor of troops to the alliance, and remains “strongly committed” to supporting the US in Afghanistan.