SHANGHAI, DEC. 23 -- A Taiwanese citizen who came to China to monitor the trial of a Chinese student activist and speak in his defense was expelled from China yesterday.

David Chien, 34, a California engineer and permanent U.S. resident, arrived in Shanghai last week, openly proclaiming on his visa application that he belongs to an organization considered subversive by Beijing.

According to a brief report in the official Shanghai newspaper Liberation Daily, Shanghai police officials ordered Chien to leave the country yesterday after he engaged in activities here in the name of the Chinese Alliance for Democracy. The government has described the group, which is based in New York and promotes human rights and democracy on the mainland, as a "counterrevolutionary" organization.

According to alliance sources, the Shanghai police detained Chien for nine hours for questioning before expelling him. They accused him of violating his visitor's visa, disturbing court business and taking part in banned activities.

Chien was barred from attending the trial Monday of Yang Wei, 32, a Chinese student who was convicted of engaging in counterrevolutionary activities and given a two-year sentence at the end of the day-long trial. Yang was arrested a year ago during prodemocracy demonstrations in Shanghai after returning to China from the United States. He holds a master's degree in molecular biology from the University of Arizona.

{In Washington, the State Department said the United States regretted Yang's sentence and hoped that "upon further review, Chinese authorities will show leniency in this case." Although foreign observers were barred from the trial, the department noted that based on its information, the principal accusations against Yang related to public criticisms of Chinese policies, including distributing pamphlets, putting up posters and mailing correspondence espousing his political views.

{"We are committed to promoting basic human rights, including the right of individuals to the free expression of their political beliefs," the department said in a statement.}

According to Wang Bingzhang, chairman of the alliance, Chien walked to the Intermediate People's Court in Shanghai Monday morning and passed out leaflets prepared by the alliance declaring Yang's innocence and calling for his immediate release.

Reached in New York, Wang said Chien argued with Shanghai court officials and tried to attend the trial but was denied permission. Chien also made a speech in front of the court building before the police arrived to take him away for questioning, Wang said.

During the questioning, Chien showed his passport and materials prepared by the alliance and told authorities he had a right to attend the trial because Beijing had said the trial would be open to the public. As a Taiwanese citizen, he also pointed out that he should be allowed to attend the trial because he is Chinese.

Chien asked several times to call the United States, Yang's parents and the U.S. Consulate in Shanghai, but his requests were denied, Wang said.