Donald Trump spoke to reporters as he met Jens Stoltenberg BRUSSELS, Belgium — US President Donald Trump launched a blistering attack on Germany at the start of a tense NATO summit Wednesday, accusing Berlin of being “captive” to Russia and demanding it and other allies immediately step up defense spending.

The two-day meet in Brussels was already shaping up to be the alliance’s most difficult in years, with Europe and the US engaged in a bitter trade spat and Trump demanding that NATO allies “reimburse” Washington for the cost of defending the continent.

European allliance members were braced for criticism from Trump on defense spending, but his furious tirade at what should have been an amicable breakfast meeting appeared to take even NATO chief Jens Stoltenberg by surprise.

“Germany is a captive of Russia because it is getting so much of its energy from Russia,” Trump said, taking particular aim at the proposed Nord Stream II pipeline.

“Everybody’s talking about it all over the world, they’re saying we’re paying you billions of dollars to protect you but you’re paying billions of dollars to Russia.”

Trump has long complained that European NATO members do not pay enough for their own defense, accusing them of freeloading on America and singling out Germany for particular criticism.

NATO officials and diplomats will try to promote an image of unity at the summit in the face of growing unease about the threat from Russia, but after Trump’s attack it may prove difficult to paper over the cracks.

The meeting of 29 Western leaders has the potential to descend into another public bust-up following a divisive and bad-tempered summit of G7 nations in Canada last month.

Trump ramped up his rhetoric ahead of the talks, explicitly linking NATO with the transatlantic trade row.

“The European Union makes it impossible for our farmers and workers and companies to do business in Europe (U.S. has a $151 billion trade deficit), and then they want us to happily defend them through NATO, and nicely pay for it. Just doesn’t work!” he tweeted as he arrived in Brussels late on Tuesday.

EU President Donald Tusk launched his own salvo against Trump on Tuesday.

“Dear America, appreciate your allies, after all you don’t have that many,” Tusk said, before reminding Trump that European troops had come to America’s aid following the September 11, 2001 attacks on the United States.