10th Mountain Division are heavy weather specialists
Uzbek President Islam Karimov told the visiting US Defence Secretary Donald Rumsfeld on Friday that US forces could use one airbase - but strictly for search and rescue, and humanitarian, missions.
He ruled out using the base - which is on the border of Afghanistan - for the launch of ground or air attacks, and said special operations forces would not be allowed into the country.
Correspondents say that too clear a signal of support for the US could cause domestic problems in Uzbekistan, where many people admire the Taleban.
The US troops are from the elite 10th Mountain Division.
They will help defend the air base, which will be used by other US units involved in search and rescue operations.
President Karimov said American troops would be allowed to fly a limited number of cargo planes and helicopters from the airfield.
It will be the first time US military have been deployed for operational duties on former Soviet territory.
Intelligence co-operation
President Karimov also said his government was ready to increase intelligence co-operation with Washington. Uzbekistan is believed to be an invaluable source of information on Afghanistan.
The Uzbek leader refused to be drawn on why he had agreed to host the US forces.
"There have been no specific quid pro quos if that's what you're looking for," he said.
"The two countries have met, the two countries have talked, the two countries have agreed that the problem of terrorism is a serious one. And we have worked out a series of arrangements that make sense from both of our standpoints."
Uzbekistan battles with its own terrorist problem.
The Islamic Movement of Uzbekistan - which also has bases in Afghanistan and is connected to Osama Bin Laden - was blamed for a series of bombings in February 1999 in the capital, Tashkent, that killed 13 and injured about 120.
But the Uzbek people are less enthusiastic about a US military presence.
Yelena Shishkina, 23, a street seller in Tashkent was worried.
She said: "American troops will go back to their homeland and the Uzbek people will remain face-to-face with the Afghan problem."