"There were early indications that China was prepared to improve its behavior as the games approached," said Howard Berman, the Democratic head of the House of Representatives foreign affairs panel.
But "the hope was short-lived, as China failed to honor these commitments," he said, citing as examples Beijing's "failed" pledges to allow greater press freedoms and improve its general human rights situation.
Reporters Without Borders announced in its annual report on China that in 2007 the government "did everything possible to prevent the liberal press, Internet users and dissidents from expressing themselves."
A recent poll by the Foreign Correspondents' Club of China found that 67 percent of foreign journalists felt China was not keeping its promise to allow freedom of reporting, Berman said.
He also cited China's deadly crackdown on protests in March and the arrest in December of Hu Jia, a leading fighter for human rights, health care and the environment, and questioned China's "ardent" support for governments in Sudan and Myanmar despite their rights records.
Beijing's support for Robert Mugabe's hardline regime in Zimbabwe was also raised, especially its veto of a UN Security Council resolution that would have imposed an arms embargo on Zimbabwe and travel and financial restrictions on the leader and other senior officials.
The House foreign affairs committee is scheduled to discuss a resolution Thursday on China's human right record in the run up to the Olympics.
The resolution wants Beijing "to immediately end its abuses of the human rights of China's citizens, including its Tibetan, Uighur, and other ethnic minority citizens and to end its support for the governments of Sudan and Burma (Myanmar) to ensure that the Olympic games take place in an atmosphere that honors the Olympic traditions of freedom and openness."
Ileana Ros-Lehtinen, the ranking Republican member in the House foreign affairs panel, said Beijing had "intensified its brutal crackdown on political dissidents and activists.
"One would wish that the motto of this year's Olympics, 'one world, one dream,' could ring true," she said. "Unfortunately, when it comes to the pursuit of democratic values and human rights, we remain a world divided with a dream unfulfilled."
Ahead of the games, Ros-Lehtinen claimed Beijing had initiated "broad and sweeping measures to silence internal criticism," allegedly detaining hundreds of practitioners of the Falun Gong spiritual sect and members of other organized movements.
"The number of reported raids and summary executions continues to rise, and the regime has even taken violent measures to discourage North Korean refugees from seeking asylum in China," she said.