"Why aren't our ambassadors speaking out?" Rep. Frank Wolf, R-Va., asked at a House appropriations subcommittee hearing that focused on human rights abuses.

"I think the ambassador ought to be fired," Wolf said.

The State Department disputed Wolf's criticism of Ambassador Michael Marine and of U.S. ambassadors generally as being in retreat from championing human rights causes.

"Certainly, we all want to see more progress made," said Tom Casey, deputy spokesman at the State Department.

But, Casey said, "the issues of promoting human rights, promoting religious freedom in Vietnam are something that is important to this administration, that the embassy works on every day."

In recent weeks, police in Vietnam have cracked down on a small band of dissidents who challenged the Communist party's monopoly on power. On Friday, a well-known Catholic priest, Nguyen Van Ly, is due to go on trial accused of crimes against the state.

Wolf also condemned China for undertaking to build what he called a palace for Sudanese President Omar al-Bashir. Sudan is a major supplier of oil to China.

On a trip to Africa earlier this year, Chinese president Hu Jintao disappointed the Bush administration by promising to help in the palace project.

Last month, the State Department in an annual report on human rights worldwide singled out the situation in Darfur, where more than 200,000 have died and an estimated 2.5 million have been displaced during four years of violence.

Wolf said he blamed both the administration and Congress for four years of genocide in the African country.

"We should be pushing aggressively," he said. But the administration and Congress are motivated in seeking trade and business around the world, rather than promoting human rights, he said.

Last week, Secretary of State Condoleezza Rice said the administration was pressing Vietnam on allegations of human rights violations.

Rice said she recently told Vietnam's foreign ministry "in no uncertain terms that human rights is going to have to be a very big part of our agenda, and we'll continue to press the case."