By Monica Whitlock
BBC News, Tashkent
A group of United States senators is in Uzbekistan to try to press for an international inquiry into the bloody events there two weeks ago.
Islam Karimov has rejected an international inquiry into the killings
Then, the army opened fire on a crowd of demonstrators in the town of Andijan, possibly killing hundreds.
But President Islam Karimov has said that no outside country can assist in establishing the facts.
He declined to meet the senators, a sign of how strained the US-Uzbek relationship has become.
Senator John McCain, leading the team, was blunt in his opening remarks.
"We are here today because we are concerned about recent events which entailed the killing of innocent people," he said.
"I believe that the United States must make this government understand that a relationship is very difficult, if not impossible, if the government continues to repress its people."
Mr McCain said an international inquiry into the killings at Andijan must take place at once, led by the Organization of Security and Co-operation in Europe (OSCE).
He was backed by the US ambassador in Tashkent, Jon Purnell, who said he had continued to urge the Uzbek government to allow an inquiry, even though President Karimov has already rejected the idea.
But how much influence the diplomatic world still has on Uzbekistan is hard to judge.
It is a sign of the times that President Karimov and all his officials refuse to meet the senators and their news conference took place in the US embassy basement.
Before Andijan, US visits were generally grand affairs, attended by top officials and given great play on state television.
Tashkent and Washington became significant partners after 11 September 2001, when the US army opened an airbase in southern Uzbekistan, close to the Afghan border.
The base is still the springboard for US operations in Afghanistan, and it is not clear what will happen to it should relations continue to sour.