US President Donald Trump on Sunday attacked as a "real loser" a US Olympic skier who said he had mixed feelings about representing America while it's riven by crisis.

Freestyle skier Hunter Hess was asked at a press conference on Wednesday how he feels about representing America at the Winter Olympics, given its acute tension over violent immigration raids and other political crises.

"There's obviously a lot going on that I'm not the biggest fan of, and I think a lot of people aren't," Hess said in Italy.

"Just because I'm wearing the flag doesn't mean I represent everything that's going on in the US," Hess added.

Hess said it "brings up mixed emotions to represent the US right now."

While it is very rare for a US president to criticise a member of the US Olympic team, Trump did so on his Truth Social platform in response to Hess' comments, displaying his penchant for attacking those who do not support him.

Trump wrote: "Hunter Hess, a real Loser, says he doesn't represent his Country in the current Winter Olympics."

"If that's the case, he shouldn't have tried out for the Team, and it's too bad he's on it. Very hard to root for someone like this," Trump said.

America's political tensions have rippled through the Games in Italy.

Italians have expressed anger that Immigration and Customs Enforcement (ICE) agents are accompanying the US team.

Vice President JD Vance was booed at the opening ceremony of the Milan-Cortina Games. (AFP)