Uzbekistan (search) indicated on Thursday that it was reconsidering the future of a U.S. airbase it hosts, threatening a key support base for the U.S.-led efforts in neighboring Afghanistan (search).

The move, which throws into doubt the American military presence in the Central Asian nation, follows an increasing chill in relations between Washington and the authoritarian Uzbek leader Islam Karimov (search).

The Foreign Ministry said the air base at Karshi-Khanabad, which U.S forces use to support operations and supply humanitarian aid to Afghanistan, was only intended for combat operations in Afghanistan during the overthrow of the Taliban (search) regime after the Sept. 11, 2001, attacks.

"Any other prospects for a U.S. military presence in Uzbekistan were not considered by the Uzbek side," the ministry said in a statement.

Uzbekistan also claimed that the United States hadn't paid takeoff and landing fees for all flights to and from the base, and had offered virtually no compensation for additional costs incurred by the Uzbek authorities for guarding the base, new infrastructure, ecological damage and inconvenience to the local population.

"In the view of the Foreign Ministry of Uzbekistan, these considerations should be central to examining the prospects of the future presence of the U.S. military force at the Khanabad air base," the statement concluded.

On Tuesday, a regional alliance led by China and Russia and including Uzbekistan called for the U.S. and its coalition allies in Afghanistan to set a date for withdrawing from several states in Central Asia, reflecting growing unease at America's military presence in the region.

U.S-led military forces have been deployed at air bases in Uzbekistan, Kyrgyzstan and Tajikistan since the Sept. 11, 2001, attacks to back up the anti-terrorist campaign in neighboring Afghanistan.

According to the U.S military, Uzbekistan hosts at least 800 U.S. troops, while 1,200 U.S.-led troops are in Kyrgyzstan. Some 200 French air force personnel are based in Tajikistan.

In Washington, several U.S. officials rejected the calls for a deadline.

On Wednesday, the U.S. Ambassador to Kazakhstan John Ordway said coalition operations in Afghanistan "are ongoing and will be for some time to come."

"Unfortunately, there are a number of challenges remaining in Afghanistan and the military contingents there remain essential in the struggle to provide that security and stability," Ordway told reporters in the Kazakh commercial capital Almaty.

Uzbekistan's ties with the United States and other Western nations have sharply deteriorated since it came under international condemnation for the harsh suppression of a May uprising in the eastern city of Andijan.

Uzbek authorities say 176 people died and deny that government troops fired on unarmed civilians but rights activists say as many as 750 may have been killed.

Karimov put restrictions on the U.S air base — located in southern Uzbekistan about 112 miles from the Afghan border after Washington joined calls by other Western nations for an international probe into the Andijan massacre.