WASHINGTON — U.S. President Donald Trump opened his European trip Wednesday by attacking NATO allies for unfairly burdening the United States with their security needs and accusing Germany of being “captive to Russia” because of business interests.

The comments came at the start of a two-day NATO summit, which White House officials insisted would highlight the strength of the alliance and the importance of cooperation between its members.

But Trump, who in recent months has frequently complained about what he sees as insufficient defense spending by other alliance members, used his first meeting with NATO Secretary General Jens Stoltenberg to again criticize the group for relying too much on American might and dollars for their security.

“Since our last meeting, commitments have been made for over $40 billion more money spent by other countries,” Trump told reporters at the meeting. “So that’s a step, but it’s a very small step. … It’s a very small amount of money relative to what they owe and to what they should be paying. And it’s an unfair burden on the United States.”

Trump also took specific aim at Germany, a recurring target of his critiques, for being “totally controlled by Russia” because of energy deals between the two countries.

“They will be getting from 60 to 70 percent of their energy from Russia and a new pipeline. And you tell me if that’s appropriate because I think it’s not, and I think it’s a very bad thing for NATO,” he said. “And I don’t think it should have happened. And I think we have to talk to Germany about it.”

He also blasted Germany for spending less of its gross domestic product on military needs than the United States does, calling them “a rich country” and asserting “they have to step it up immediately.”

Trump’s salvo came just hours after the Senate overwhelmingly passed a bipartisan measure expressing support for NATO and its mutual self-defense clause. It’s one of several legislative moves lawmakers have planned that counter Trump’s aggressive message.

Senate Armed Services Committee ranking member Sen. Jack Reed, D-R.I., proposed the measure, calling America’s commitment to NATO “ironclad” and Trump’s planned meeting with Russian President Vladimir Putin later in the week “ill-advised.”

Lawmakers have echoed the fears of European allies that Trump may, during the trip, agree to alter America’s defense posture in Europe by moving U.S. troops or pulling them out of joint exercises. Several have said he must not concede on Russia’s election meddling or annexation of Crimea.

Even before the meeting, ties between America and its European allies have been strained. Trump has repeatedly questioned the relevance of the alliance along with his insistence that other countries fulfill their goal of spending 2 percent of GDP on defense by 2024.

The comments rattled several European allies, who dismissed Trump’s assertions that the U.S. shoulders most of their security responsibilities.

“America does not have and will not have a better ally than Europe,” European Council President Donald Tusk said in a speech following Trump’s remarks. “Today, Europeans spend many times more on defense, many times more than Russia, and as much as China. You can have no doubt that this is an investment in common European and American defense and security.

“America: Appreciate your allies. After all, you don’t have that many.”