US President Donald Trump repeated accusations on Saturday that Germany was not pulling its weight in international defence funding.
"The idea of a European Military didn't work out too well in W.W. I or 2," Trump tweeted.
"But the U.S. was there for you, and always will be. All we ask is that you pay your fair share of NATO. Germany is paying 1% while the U.S. pays 4.3% of a much larger GDP - to protect Europe. Fairness!"
The goal for NATO is for each member state to give 2 per cent of its GDP to fund the alliance.
Trump has long criticized allies over lagging military expenditure, at times causing them to doubt Washington's commitment to collective defence.
He has blasted allies on Twitter before for failing to meet the alliance's defence spending target of 2 per cent of gross domestic product (GDP), and said the target should be increased to 4 per cent of GDP instead.
