Kyrgyzstan's prime minister said Wednesday that his government is not in talks with Washington on the possibility of allowing U.S. forces to remain at an air base that provides support for military operations in Afghanistan.

Prime Minister Igor Chudinov spoke a day after the Pentagon reported progress in negotiations on maintaining the U.S. presence at Manas air base.

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"There was not, and is not, any order and authorization for any government official to conduct such negotiations," Chudinov told reporters.

The U.S. has leased the base in the ex-Soviet republic since 2001. It is a transit point for 15,000 troops and 500 tons of cargo each month to and from Afghanistan.

Kyrgyzstan ordered the base closed in February, citing what it said was inadequate financial compensation and other concerns, and gave U.S. forces six months to leave. U.S. officials suggested Russia, which has bristled at the U.S. military presence in former Soviet Central Asia, influenced the decision.

Losing the Manas base would pose a serious challenge to President Barack Obama's plan to send 21,000 more American forces into Afghanistan this year to fight surging Taliban and Al Qaeda violence.

A senior U.S. administration official said last month that Kyrgyzstan had invited the U.S. to hold discussions on the possibility of the lease agreement remaining in force.

On Tuesday, Pentagon spokesman Geoff Morrell reported progress, saying, "I think we see reason for hope there, that that can be worked out." He would not describe the negotiations in detail, but said he hoped agreement on a lease was getting closer.

Announcement of the closure came shortly after Russia, which also has an air base in Kyrgyzstan, pledged more than $2 billion in aid, loans and investment to Kyrgyzstan.

Some Kyrgyz analysts have speculated that U.S. forces may be able to continue using Manas base under a different status, but Chudinov also denied that possibility.

He said the decision on the closure — which was adopted by parliament and approved by President Kurmanbek Bakiyev, who first announced it at Russian President Dmitry Medvedev's side — remains in force and unchanged.

Bakiyev and other government officials had complained that the United States ignored repeated demands for an increase in the $17.4 million annual rent for the base. Defense Secretary Robert Gates had said the U.S. would be willing to pay more, within reason.