The US base has been the focus of local protests
Kyrgyzstan's government has submitted a decree to parliament for the closure of a key US air base in the Central Asian state, Kyrgyz officials say.
The move was prompted by popular disapproval of the base, government spokesman Aibek Sultangaziyev said.
US officials say they have received no notification of the closure, and are talking to the Kyrgyz government.
The air base supports US and Nato operations in Afghanistan and is the only US base in Central Asia.
Its closure would be a major blow for those operations, the BBC's Richard Galpin in Moscow says.
The announcement comes at a critical moment, just as the new administration of US President Barack Obama plans a sharp increase in the number of American troops in Afghanistan.
For Russia, on the other hand, it is a significant diplomatic victory as it seeks to reassert its influence in all former Soviet republics and beyond, our correspondent says.
"A draft decree on terminating the agreement on the US airbase has been sent to parliament," said Aibek Sultangaziyev.
"It is up to parliament now to decide when to hold discussions on this."
The spokesman told the BBC that the United States would have six months to close down operations after the measure was approved.
The move follows a statement by President Kurmanbek Bakiyev that the Manas air base would close.
President Bakiyev made his announcement on Tuesday in Moscow, where he was promised more than $2bn (£1.4bn) in Russian aid.
He said the Manas base - set up in 2001 to assist the US military operation against al-Qaeda and the Taleban in Afghanistan - was only meant to be open for two years at the most.
Kyrgyzstan 'to shut' US air base
But perhaps more importantly, he made it clear the Americans had not been willing to pay what Bishkek regards as the right price to keep the base open, our correspondent says.
The Russian government has stepped in with a huge financial package for Kyrgyzstan - $2bn in loans and another $150m in aid.
US officials appear not to have known about Mr Bakiyev's decision, with a US embassy spokesman telling reporters on Wednesday: "The embassy does not know anything about this at the moment."
In a statement, the embassy said: "We have been in discussions with Kyrgyz authorities on the future of Manas air base. These discussions will continue."
Meanwhile, Colonel Greg Julian, US spokesman in Afghanistan, told the Associated Press that Mr Bakiyev's statement was "political positioning".
Last month, the top US military commander for the Middle East and Central Asia, Gen David Petraeus, held talks in Bishkek about the future of Manas.
He said afterwards that the closure of the base had not been discussed.