Watch: Police remove climate protesters from US Open after 50-minute delay

NEW YORK - Coco Gauff’s U.S. Open semifinal victory over Karolina Muchova was delayed by 50 minutes because of a disruption by four environmental activists in the Arthur Ashe Stadium stands Thursday night. One protester glued his bare feet to the concrete floor.

Gauff was leading 1-0 in the second set when play was halted. She would go on to win 6-4, 7-5.

"I always speak about preaching about what you feel and what you believe in. It was done in a peaceful way, so I can’t get too mad at it. Obviously I don’t want it to happen when I’m winning up 6-4, 1-0, and I wanted the momentum to keep going," said Gauff, a 19-year-old from Florida. "But hey, if that’s what they felt they needed to do to get their voices heard, I can’t really get upset at it."

Security guards and, later, more than a half-dozen police officers went over to confront the protesters, who were wearing shirts that read, "End Fossil Fuels." The U.S. Tennis Association said three of the protesters were escorted out of the stadium without further incident, but it took longer to remove the person who stuck his feet to the ground.

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The USTA added that NYPD and medical personnel were needed in order to safely remove that person. All four activists were taken into police custody.

Muchova said that, initially, she "thought it was, like, fans screaming, cheering."

A group called Extinction Rebellion said it was responsible for the protest.

One of the protesters, who identified himself only as Ian, told The Associated Press the group believes the U.S. Open has sponsorship deals with corporations whose policies are contributing to global warming.

"We are not trying to harm the athletes in any way. We have nothing against the sport," he said. "But we are really trying to draw attention to an issue here that there will be no tennis left for anybody in the world to enjoy."

Spectators were asked to move away to clear a path for the police, who were cheered by fans sitting near the section where the disruption happened.

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Gauff sat on her sideline bench for a bit during the break in the match, eating fruit out of a plastic container, before then getting some tennis balls and hitting a few practice serves. Muchova was briefly visited by a trainer during the interruption.

"We didn’t know how long it was going to take. We were talking to the supervisor and security. You know, they (said) it could be as quick as five minutes or as long as an hour," Gauff said. "It was tough to figure out if we stay warm or conserve energy."

Eventually, both players headed toward the locker room as the delay continued. Gauff sat on a treadmill, a towel draped over her lap, while chatting with members of her team.

"I just wanted to get off the court and then keep myself little warmed up and not just to stand there," Muchova said.

It is the latest in a recent series of protests at sporting events — and tennis, in particular — related to the use of fossil fuels.

"Throughout history, moments like this are definitely defining moments. I believe, you know, in climate change. I don’t really know exactly what ... they were protesting. I know it was about the environment. I 100% believe in that. I think there are things we can do better," Gauff said at her post-match news conference.

"Would I prefer it not happening in my match — 100%, yeah," she said. "I’m not going to sit here and lie."

At Wimbledon in July, two matches were interrupted when environmental activists jumped out of the stands at Court 18 and scattered orange confetti on the grass.

At a U.S. Open tune-up tournament in Washington last month, about a dozen people were asked to leave the site after chanting and displaying signs protesting the use of fossil fuels.

"We see it here and there on some occasions. Not just with tennis," Muchova said. "It is what it is. ... What can we do about it?"

Gauff and Muchova, a 27-year-old from the Czech Republic, were both playing in the semifinals at Flushing Meadows for the first time.

Their match was the first of the evening. The other women’s semifinal, between Aryna Sabalenka of Belarus and Madison Keys of the United States, began shortly after Gauff’s victory finished. It ended at nearly 1 a.m., with Sabalenka winning 0-6, 7-6 (1), 7-6 (10-5) to reach her second Grand Slam final.

Gauff and Sabalenka will play each other for the championship in Ashe on Saturday.