Washington has described as "unfair" the trial in Uzbekistan of 15 men convicted on Monday of leading an uprising in the town of Andijan.
The 15 defendants all pleaded guilty on the first day of the trial
The court found the men guilty of trying to oust the government and set up an Islamic state, and jailed them for between 14 and 20 years.
Security forces suppressed the May unrest with massive force, leaving hundreds of people feared dead.
Critics have denounced the court's proceedings as a show trial.
"We believe that these convictions are based on evidence that isn't credible and a trial that isn't fair," US state department spokesman Adam Ereli said on Monday.
He said the US had expressed misgivings about the case from the beginning, and the Uzbek government had not responded positively to appeals by the US and others for an international investigation of the events in Andijan.
The European Union announced a year-long visa ban on 12 senior Uzbek officials, including the defence and interior ministers, who it said were "directly responsible" for the violent suppression of the Andijan revolt.
In a statement, the EU's member states said the measure was taken because of Uzbekistan's refusal to allow the outside inquiry.
It also banned exports of arms and other equipment that might be used for "internal repression".
But Uzbek President Islam Karimov received a warmer welcome in Moscow, where he and Russian President Vladimir Putin reached an agreement on defending each other in the event of foreign aggression.
"In case of aggression committed against one of the parties by a third state, it will be viewed as an act of aggression against both countries," according to the document signed.
"We understand that Russia has always been and will remain a stronghold for us and a central ally," Mr Karimov said after signing.
The Uzbek government says 187 people, mostly "terrorist organisers", died during the Andijan unrest.
But human rights groups say 500 or more civilians may have been killed, shot by Uzbek security forces.
Judge Bakhtyor Jamolov said the convicted men - 12 from Uzbekistan and three from neighbouring Kyrgyzstan - were guilty of "terrorism, attempts to overthrow the constitutional order, aggravated murder and the seizure of hostages".
Five received 20-year sentences.
The Uzbek government says that Islamic radicals, trained in the neighbouring republic of Kyrgyzstan, organised a jailbreak in Andijan, seized many hostages and took over the local administration.
Witnesses, human rights groups and the United Nations say that Uzbek troops then crushed what they say was an anti-government demonstration.
The fact that the defendants all confessed their guilt on the first day raised concerns that the confessions might have been obtained by torture.
A former Uzbek interior ministry employee has told the BBC that beatings or psychotropic drugs are often used to force confessions from suspects - an allegation denied by the Uzbek government.