Human Rights Watch (HRW) said the world is expecting America to send out the right message about democracy during its defence secretary's visit to the central Asian country on Tuesday.
Uzbeksitan, a key US ally, has been hammered by human rights groups for political repression, the use of state-sponsored torture, and lack of democratic freedoms.
"The Uzbek government has promoted itself as a partner in the US-led campaign against terrorism," said Tom Malinowski, Washington advocacy director for HRW.
"Donald Rumsfeld should tell [Uzbek President Islam] Karimov that real partners in that fight abide by the rule of law, and give people peaceful avenues for expressing themselves."
After the 11 September attacks on the US, the Bush administration established an air base in Uzbekistan to facilitate its attack on Afghanistan and dramatically
increased assistance to the Uzbek government.
But last month, the US State Department decertified Uzbekistan for aid because it had made no progress towards ending police torture and other abuses.
The US assistance programme helps former Soviet republics destroy and avoid proliferation of nuclear, chemical and biological weapons.
"The Uzbek government has promoted itself as a partner in the US-led campaign against terrorism. Donald Rumsfeld should tell (Uzbek President Islam) Karimov that real partners in that fight abide by the rule of law, and give people peaceful avenues for expressing themselves"
Human Rights Watch
Later this spring the Bush administration will have to decide
whether to certify Uzbekistan for broader assistance programmes.
"Uzbekistan still has time to make improvements in advance of the spring certification," said Rachel Denber, acting executive director of Human Rights Watch's Europe and central Asia division.
"Rumsfeld should tell Karimov that the Pentagon's own programmes are on the line and that they won't go forward unless the Uzbek government shapes up."
HRW said Rumsfeld's failure to deliver a consistent message about US policy in neighbouring Azerbaijan during his December 2003 visit to Baku undermined efforts to promote democracy and human rights in the country.
The visit came just six weeks after the Azeri government had
rigged the presidential elections and launched a brutal crackdown on the political opposition.
Yet, Rumsfeld openly congratulated Ilham Aliev on his election victory and refused to answer questions about whether the presidential elections had met international standards.
"Many will now be looking to Rumsfeld to deliver a consistent
message on US policy towards Uzbekistan," Denber said.
"Will he clearly say that repressive Uzbek government policies are wrong and will ultimately undermine stability in that country? Or will he stay silent on political repression and torture, sending an unwitting green light to the government?"