The United States is formally protesting China's decision to deny US Winter Olympic champion and Darfur anti-violence campaigner Joey Cheek an entry visa, White House spokeswoman Dana Perino said today.

"We were disturbed to learn that the Chinese had refused his visa," said Perino, traveling with President George W. Bush in Asia.

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"We are taking the matter very seriously. We have sent in our embassy in Beijing to demarche the Chinese. That is where we're going to say we are concerned about this and want you to reconsider the actions," Perino said.

"We hope they change their minds," she said.

Former Olympic speedskater Cheek had his visa revoked by Chinese authorities today, hours before he was set to travel to Beijing to promote his effort urging China to help make peace in the war-torn Darfur section of Sudan.

Cheek, the president and co-founder of a collection of Olympic athletes known as Team Darfur, was planning to spend about two weeks in China, when he received an unexpected call from authorities.

The 2006 American gold medalist said they told him they were denying him entrance into the country and were "not required to give a reason."

"I didn't see it coming," Cheek said. "I figured once they gave me a visa, I wouldn't imagine they wouldn't allow me to come in later. That was a big shock. I wasn't expecting to get a call the evening before I was leaving for Beijing."

One of Cheek's key initiatives was urging the international community to persuade Sudan to observe the ancient tradition of the Olympic truce during the Beijing Games.

More than 200,000 people have been killed and 2.5 million displaced in fighting in the western Sudanese region since ethnic African tribesmen took up arms in 2003.

The Olympic truce dates to the ancient games in Greece, when fighting was halted to ensure athletes had safe passage to travel to and from the competitions. Attempts to revive the truce in modern times have met with only modest success, most notably in the Balkans during the 1992 and 1994 Games.

Cheek said he has been upset by China's treatment of athletes involved in his cause and thinks the International Olympic Committee's rules that prohibit political protest go against the spirit of the games.

"I've been pretty unimpressed with the IOC's efforts in protecting athletes, for giving them any options," Cheek said.