A notice to leave Karshi-Khanabad air base, also known as K2, was delivered on Friday by a courier from the Uzbek Foreign Ministry to the US embassy in Tashkent, the Washington Post reported in its Saturday edition, citing an unnamed senior US official involved in Central Asia policy.
Asked about the report, Pentagon spokesman Glenn Flood said early on Saturday, "We are aware of the diplomatic note to the US embassy on the issue of K2 air field and we are working with the State Department, evaluating the note to see exactly what it means."
State Department officials could not be reached for comment.
Uzbekistan will give the United States 180 days to move aircraft, personnel and equipment, the newspaper said. It added the United States expected Uzbekistan to follow through on the eviction notice.
The action would create logistical problems for US operations in Afghanistan, the newspaper said.
Scores of flights have used the air field to transfer humanitarian goods that are then taken by road into northern Afghanistan, it said.
"The air field has been important to us and the US allies in operations over there," Flood said.
The United States has regarded its bases in Uzbekistan and Kyrgyzstan as vital for operations in Afghanistan.
However, the US presence in Central Asia has caused tensions with Russia and China, which joined the five ex-Soviet Central Asian states this month to demand a US deadline for leaving the bases.
"The air field has been important to us and the US allies in operations over there"
US relations with authoritarian Uzbekistan also have been strained by the Uzbek government's bloody suppression in May of a rebellion in the eastern town of Andizhan, which drew US criticism.
This past Monday, however, US Defence Secretary Donald Rumsfeld responded to a question about maintaining the base in Uzbekistan by saying, "We've had a good relationship. It's a good relationship now."
He was speaking during a visit to Kyrgyzstan, whose defence minister said the United States would not need a military presence in that country once stability had returned to Afghanistan.