Tensions between the United States and Europe took a new turn on Monday as Belgian officials and European soccer figures expressed outrage over the reinstatement of a banned American player before an evening World Cup game against Belgium.

The trans-Atlantic relationship had already been under strain for much of the past year and a half, and is poised to face another test just this week as leaders head to Turkey for a closely watched NATO summit. Now many in Europe are also outraged over what they see as the American president’s meddling in soccer.

President Trump started 2026 with threats to take over Greenland, an autonomous territory of Denmark, a NATO member, a move that rattled the foundations of the alliance. He has also assailed European leaders over the war in Iran, saying they have not supported the United States in that conflict.

His administration has threatened to draw down troops stationed in Europe, which are seen as a critical deterrent to Russia, and he has lashed out at countries he says aren’t spending enough on their militaries.

European leaders have been hoping to use the NATO summit, which begins on Tuesday, to demonstrate how much more they are spending on their militaries, with a goal of keeping Mr. Trump and the United States engaged in the military alliance. The stakes are high as Russia increases its attacks on Ukraine, with a strike last week leading to the death of 31, and one on Monday morning that killed at least 12 people.

Last week, Mr. Trump called the president of FIFA, Gianni Infantino, and asked the association to review the suspension of the top goal scorer in the World Cup for the American team, Folarin Balogun, after he was given a red card banning him from a game, according to people familiar with the conversation.

Belgian officials expressed dismay after FIFA, the world soccer governing body, announced on Sunday that it was lifting the one-game suspension against Mr. Balogun. Maxime Prévot, Belgium’s foreign minister and a former soccer referee, said in statement on Monday that the decision might undermine FIFA’s expressed commitment to fair play.

“This decision clearly raises many questions,” Mr. Prévot said. “If a phone call really is what explains this incomprehensible decision, it would amount to undermining the most basic rules of soccer and sports.”

The Royal Belgian Football Association said in a statement that it “has no alternative but to challenge the player’s eligibility for the upcoming match,” adding that it was “deeply concerned” by the process.

UEFA, European soccer’s governing body, said in a statement that FIFA’s reversal had “crossed a red line,” calling it “an unprecedented, incomprehensible and unjustifiable decision.”

While the Belgian team has been granted the right to appeal FIFA’s decision, there was no guarantee that a ruling would be possible before kickoff on Monday at 8 p.m. Eastern time.

The decision by FIFA was highly unusual and a boost to the American team. Mr. Infantino has courted Mr. Trump, and last year awarded him the first FIFA Peace Prize as the president campaigned, but failed, to win the Nobel Peace Prize.

Speaking at the White House on Monday, Mr. Trump confirmed that he had called Mr. Infantino to protest the red card and ask for “a review.” He said he had watched the game and determined, as a sports lover, “that wasn’t a foul, that wasn’t even an infraction.”

The president attempted to downplay his intervention, saying that during his conversation with Mr. Infantino he “didn’t tell him what to do.”

“I can’t tell him what to do, and I don’t believe he made the decision,” Mr. Trump said. “I think it was a committee that made the decision, and they made the right decision, because number one, it wasn’t a foul, and you want to see a game with your best players.”

The U.S. ambassador to Belgium, Bill White, defended FIFA’s decision in a post on X on Monday and said, “President Trump would never interfere with the inner workings of FIFA.”

A key question is whether the drama will heighten diplomatic tensions, and worsen an already challenged relationship between Europe and the United States, heading into a pivotal week.

Mujtaba Rahman, managing director for Europe at the Eurasia Group, said that he didn’t think the soccer controversy would be enough to further destabilize the trans-Atlantic relationship.

“But it does serve as a timely reminder to European governments about how Trump operates,” he said in a written response to questions. “Unconstrained by rules or norms, and the ruthless pursuit of an America first policy in everything he does.”

Still, European officials who have bitten their tongues throughout situations that they have seen as unacceptable — threats to a sovereign territory, a damaging trade war — may struggle to do so with when it comes to the game.

When asked for a comment on FIFA’s decision, a spokeswoman for Belgium’s prime minister, Bart De Wever, referred questions to an Instagram post attributed to the prime minister’s cat.

“Red card?” the post says, in Dutch. “I’m going to play anyway!”

Political leaders across Europe are likely to see the soccer situation as another example of “how the U.S. is a lawless, unconstrained place under Donald Trump,” said Jacob Funk Kirkegaard, an analyst at the Belgian think tank Bruegel.

He said that in the longer term, it’s likely to make it even harder for leaders on the European right, who had already been distancing themselves from Mr. Trump, to align with the American leader.

But in the near term, European leaders “urgently need” Mr. Trump’s support at the summit in Ankara, because Ukraine needs American-made Patriot air defense systems as it fights against Russia.

“So they will not be picking a fight,” he added.

Koba Ryckewaert contributed reporting from Brussels, and Erica L. Green from Washington.