The Nobel Prize-winning body on Monday applauded the US State Department's efforts but said they were compromised by US failures to respect the rights of prisoners in Iraq and detainees in Guantanamo Bay.
"As long as the White House continues to flout international law and blatantly disregard the Geneva Conventions, many of its policies to promote democracy and human rights will be greeted with deep scepticism," it said.
Alexandra Arriaga, director of government relations for Amnesty International USA, said American moral authority was diminished by continuing reports of judicial abuses by US authorities.
She said the US administration's overall record made the State Department's report in its rights achievements "tantamount to a business ethics manual published by Enron", referring to the failed and discredited energy giant.
The US State Department in its report - focusing on Washington's efforts to improve human rights in 98 nations - criticised the rights records of Pakistan and China.
"As long as the White House continues to flout international law and blatantly disregard the Geneva Conventions, many of its policies to promote democracy and human rights will be greeted with deep scepticism"
The report credited Pakistan with some human rights improvements but a continuing poor record.
It said Pakistan's President Pervez Musharraf's government had amended the country's constitution to strengthen his powers at the expense of the National Assembly and that the military remained heavily engaged in politics.
It also cited Musharraf's decision to continue as the army chief, saying that had stirred political debate.
China was even more heavily criticised in the report for suppressing political, social and religious groups as well as individuals.
Beijing has amended its constitution to protect human rights and has adopted legal reforms for monitoring the government. But the report said "it is unclear how or to what extent the constitutional amendment and other legal reforms will be enforced".
President George Bush, Vice-President Dick Cheney and other senior administration officials constantly raise human rights issues in their meetings with Chinese leaders, the report said.