“Every athlete competing at the 2019 Pan-American Games commits to terms of eligibility, including to refrain from demonstrations that are political in nature,” Mark Jones, a committee spokesman, said in the statement.

“In this case, Race didn’t adhere to the commitment he made to the organizing committee and the USOPC,” the statement continued. “We respect his rights to express his viewpoints, but we are disappointed that he chose not to honor his commitment.”

Mr. Jones said committee leaders were reviewing what had happened and “what consequences may result.”

Mr. Imboden said he was aware that his action could have repercussions.

“To lose fencing for me is the only thing in my life, other than my loved ones, family and friends, that would affect me greatly,” he said. “So to hear that it is something that could be affected, obviously, scares me a lot. But I don’t regret my actions.”

Friday was not the first time that Mr. Imboden, who earned a bronze medal at the 2016 Olympics, had taken a knee at a fencing event. In 2017, he and a teammate knelt during a ceremony at the Pharaoh’s Challenge men’s foil fencing World Cup in Cairo.

In a January interview with Pianeta Scherma, an Italian fencing website, Mr. Imboden said kneeling was his way of communicating his beliefs about his country. “It’s important to speak out and to stand up for people who don’t have a voice,” he said.

Mr. Imboden, who has been fencing for 16 years, said on Sunday that he was not sure he would kneel again. “I think everyone has a right to express how they feel, and obviously I am speaking about something that I knew was touchy,” he said. “I have to accept that.”