WASHINGTON — United States officials have expressed concern about security at the Winter Olympics in South Korea in February, initially raising the possibility of withdrawing from the games but later insisting that American athletes will compete.

The American envoy to the United Nations, Nikki R. Haley, said on Wednesday that it was an “open question” whether American athletes would be able to attend the Winter Games, given the tensions on the Korean Peninsula.

Sarah Huckabee Sanders, the White House press secretary, echoed Ms. Haley’s remarks during a briefing for reporters on Thursday, saying that “no official decision has been made” about participating in the Olympics. Asked about whether the reason is security concerns, she said “absolutely.”