Germany owes NATO 'vast sums': Donald Trump

US President Donald Trump on Saturday accused Germany of owing "vast sums of money" to NATO, and said Berlin should pay Washington more for defense, a day after meeting Chancellor Angela Merkel.

The two leaders showed little common ground Friday over a host of thorny issues, including NATO and defense spending.

On Saturday, Trump tweeted: "Germany owes vast sums of money to NATO & the United States must be paid more for the powerful, and very expensive, defense it provides to Germany!"

He made the statement in a series of tweets from his Mar-a-Lago base in Florida on Saturday morning.

Trump, after a video appeared to show him ignoring Merkel's request to shake hands at a photo opportunity, said: "Despite what you have heard from the fake news, I had a Great meeting with German Chancellor Angela Merkel.

"Nevertheless, Germany owes vast sums of money to NATO & the United States must be paid more for the powerful, and very expensive, defense it provides to Germany!"

Prior to his inauguration, Trump declared NATO "obsolete" but has since modified his stance, telling European leaders the alliance remains of strategic importance.

Only the US and four other members currently reach the alliance's benchmark of spending 2 per cent of GDP on defence.

Germany spends 1.23 per cent, but this is being increased.

Trump said during the Chancellor's visit he was encouraged to see Germany increasing the figure.

He said: "Many countries owe vast sums and it is unfair". James Mattis, the US Secretary of Defence, told European leaders at a NATO summit in February his country would "moderate its commitment" to the group unless member states put in more money. At the time he said: "No longer can the American taxpayer carry a disproportionate share of the defence of Western values.

"Disregard for military readiness demonstrates a lack of respect for ourselves, for the alliance and for the freedoms we inherited, which are now clearly threatened," he had said. Trump and Merkel encountered each other for the first time on Friday and initially met with US and German business leaders to discuss modelling a US vocational training programme on Germany's apprenticeship scheme, as an alternative to university education.