WASHINGTON (Reuters) - Foreign journalists covering the Beijing Olympics must take care to avoid placing Chinese assistants and news sources at risk of arrest when covering sensitive topics, a U.S. watchdog group said on Thursday.

The Committee to Protect Journalists also called on the International Olympic Committee to press China to honor promises of press freedom for the more than 21,500 foreign reporters covering the August 8-24 games -- a pledge it said authorities ignored during recent unrest in Tibet.

"Past experience has shown that China tends to err on the side of heavy-handedness when it comes to media control and threats to the country's image as a unified nation," said the New York-based committee in a report.

"Reporters traveling to China should be aware of the risks to people they interview or hire, as well as the dangers they face themselves."

The report -- "Falling Short" -- said a 2001 pledge to impose no restrictions on foreign media, which helped Beijing win the right to host the 2008 Olympics, was not being upheld.

"Even at this late date, insist that the Chinese government fully meet its promises of press freedom for the 2008 Olympic Games," the committee advised the IOC.

The promised press freedoms in China -- which do not apply to domestic media and expire after the Olympics -- were widely ignored during political unrest in Tibet in March, when scores of journalists were turned away by authorities, it said.

The report said foreign reporters who run afoul of Chinese authorities faced "more inconvenience than hardship" and generally few long-term repercussions.

But ethnic Chinese and other Asian reporters had been treated harshly in some cases and Chinese translators or other helpers asked to work on sensitive topics could face trouble, it said.

"Reporters who ask Chinese hires to arrange meetings with activists or to organize a visit to an AIDS village must realize that they could be putting their Chinese colleagues at risk," it said.

"These assistants might not be punished until after the Games, when the world's attention has moved on."

The report listed as examples of sensitive topics problems associated with the Olympics, the Buddhist Tibet or Muslim Xinjiang regions, protests over social or environmental issues, HIV/AIDS patients, crackdowns on North Korean refugees and everything involving the outlawed Falun Gong spiritual group.

(Reporting by Paul Eckert; Editing by Eric Beech)