President Donald Trump unleashed his harshest broadside yet against a European ally on Wednesday, accusing Germany of being "totally controlled by Russia" and of not meeting its obligations to the NATO alliance.

"Germany, as far I’m concerned, is captive to Russia," Trump said.

Trump's extraordinary rhetoric signaled that he would continue his aggressive, America-first attitude toward the United States' closest allies – even as he himself prepares to meet with Russian President Vladimir Putin next week in an effort to improve U.S.-Russian relations.

Speaking to reporters after Trump’s remarks, German Chancellor Angela Merkel shot back that she would not be lectured about Russian control of Germany, having grown up in the Soviet-dominated East Germany.

“I have experienced myself how a part of Germany was controlled by the Soviet Union," she said, without mentioning Trump by name.

Trump's verbal attack on Germany came in his first official event in Brussels Wednesday, setting a combative tone for the two-day summit of the alliance in Brussels. He leaves Brussels for two days in London Thursday, followed by a weekend in Scotland and his summit with Putin in Helsinki next Monday.