Bryan Whitman, a Pentagon spokesman, said on Thursday that the US is still hopeful that the base could be kept open.
"We're still very much engaged," he said.
Following Kyrgyzstan's announcement, Russia has said it will start allowing non-lethal US military supplies for Afghanistan to cross its territory.
Sergei Lavrov, Russia's foreign minister, said: "We are now waiting for the American partners to provide a specific request with a quantity and description of cargo, and as soon as they do do that we will issue relevant permissions,'' he said.
Hamish MacDonald, Al Jazeera's correspondent in Afghanistan, said the notion of the US using Russia for a supply route was an important development.
"This is incredibly significant because it illustrates just how desperate the US and Nato forces are to find a supply route," he said.
"The Americans have had to go cap in hand to Russia and say 'we need your help'.
"If this goes ahead US and Nato may find themselves dependent on a good relationship with Russia."
MacDonald added that a new supply route from Afghanistan to Russia could create a new target for Taliban wishing to attack US forces.
The original deal between the US and Kyrgyzstan gives Washington six months to shut down the base after being informed of its closure by the government.
The Kyrgyz government's remarks came despite parliament not voting on the proposal until next week.
Approval is seen as a formality as the chamber is controlled by supporters of the president.
"The issue is now with parliament which must cancel the agreement on the base with the United States," Sultangaziyev said.
Kurmanbek Bakiyev, Kyrgystan's president, announced that the base outside the capital, Bishkek, would close after he secured $2bn of Russian aid during talks with Dmitry Medvedev, his Russian counterpart, in Moscow.
However, Igor Chudinov, the Kyrgyz prime minister, has denied that the move was linked to Russia's aid package.
"Talks on Russian aid have been going on for two years, and they were in no way related to the issue of the removal of the air base from Kyrgyzstan," he said.
He said that the Kyrgyz government did not approve of the way the war in Afghanistan was being conducted.
Whitman also said it was unlikely that Russia was attempting to undermine the US presence in the region.
"It certainly doesn't make any sense for Russia or any other country in the region to try to undermine the international effort to bring stability to Central Asia," he said.
"They [Russia] have been very consistent in their public statements in the past about supporting the international effort to bring stability in Afghanistan as well as the region."
About 30,000 more US soldiers are expected to be sent to Afghanistan in 2009 as the administration of Barack Obama, the US president, plans to shift its military focus away from Iraq.
Tajikistan, another central Asian nation, has offered its airspace for the transport of non-military equipment to Afghanistan as the US and military alliance search for alternative supply routes.
"The [Tajik] president confirmed his readiness to offer thecountry's airspace for non-military Nato supplies bound for Afghanistan," Tracey Ann Jacobson, US ambassador to Dushanbe, said on Friday.
"This necessity emerged after a decision was made to increase the number of troops in Afghanistan."
Supply lines to Nato and US-led troops in Afghanistan have been hit by attacks on convoys in neighbouring Pakistan and the closure of the Manas base would cause further problemsbility.