The parliament in Kyrgyzstan has voted to evict U.S. forces from the Manas air base the United States has leased since 2001.  

The Manas air base is located in northern Kyrgyzstan, not far from the capital Bishkek.  It is the only military base leased by the United States in Central Asia and plays a critical role in the U.S. and NATO war effort in Afghanistan.

Analysts say Manas' role has increased since the Uzbek government in 2005, pressured by Russia, evicted U.S. troops from the Karshi-Kanabad airfield - known as K-2.

Last year, more than 11,000 aircraft were refueled over the skies of Afghanistan by tankers based at Manas.  More than 170,000 soldiers have transited in and out of Afghanistan through the air base, and more than 5,000 tons of cargo have made their way to that country through Manas.

Andrew Hoehn with the RAND Corporation in Washington said Manas is very important for U.S. military flights coming from Europe.

"And to connect from Europe then into Afghanistan, it is important to have a facility in Central Asia or thereabouts to be able to put the long-range transportation aircraft, to land them, to be able to re-load them in terms of using shorter-range transportation aircraft to get in and out of Afghanistan.  So some facility in that region is very important in terms of the overall effort.  And, of course, if the effort is going to be increasing, then that grows in importance as well," he said.

Now the Kyrghiz government, backed by the parliament, has decided to evict U.S. forces from the air base.   

Is Russia behind the move?

Many experts say Russia is behind the move, because the decision followed Moscow's announcement that it will give more than $2 billion in aid to Bishkek.  Russian and Kyrghiz officials have denied any link between the aid and the closing of the air base.

Analysts say the Kyrghiz government's decision was made at a terrible time for the United States, when President Barack Obama has decided to send 17,000 more troops to Afghanistan in the months ahead - in addition to the 38,000 already in the country.  The new troops will be sent to southern Afghanistan to fight a Taliban insurgency.  

Viable alternatives:  Khyber Pass

Experts say the United States has to look for alternative supply routes into Afghanistan, especially since the main land route through Pakistan's Khyber Pass has been subject to insurgent attacks.

Jason Lyall at Princeton University said there are several options - including through Pakistan.

"One is just to expand the land route and ship everything by land through the Khyber Pass.  That is obviously dangerous and much slower.  There are several other options.  If they cannot get K-2 [Karshi-Kanabad] opened in Uzbekistan, there is a possibility of flying things into Tajikistan and then moving it by land from Tajikistan and through the Pyanzh River Valley.  There is a bridge system there that has been put in place.  It cannot handle a lot of traffic, but it could pick up some of the excess that Manas [air base] would have handled," he said. 

Other Alternatives: Tajikistan, central Asian nations

Michael Williams of the University of London said the United States could try to reach an agreement with Tajikistan or other central Asian countries.  

"The irony of the fact is that most of these countries have terrible human rights records; they are not democracies.  And, of course, what NATO and the United States are trying to do is to create a democracy [in Afghanistan] that respects human rights.  The irony really is not lost there," he said. 

The direct route:  Afghanistan

But Jason Lyall said there is another option.

"The other possibility is to simply bypass Central Asia entirely and ship everything into Bagram Air Force Base in Afghanistan.  The problem with Bagram is that it is incredibly crowded right now because that is one of the central hubs for all of the aircraft flying within Afghanistan and the weather is very poor.  So they are trying to expand that Air Force base now and trying to give it an increased capacity," he explained.

Analysts say cargo and military planes could also fly into the northern airfield at Mazar-i-Sharif. 

What about Iran?

Michael Williams of the University of London added that the Americans could take a daring approach.

"There is also the fact that they could talk to Iran, which could be quite a coup.  Of course, the Iranians are incredibly interested in making sure Afghanistan is stabilized.  And, therefore, I suppose if the Obama team really wanted to take a big, bold step, they could talk to Iran about ensuring some sort of supply [route].  I doubt that will happen, however," he said.

Whatever option is chosen, analysts say the United States must act quickly in order to ensure an uninterrupted flow of supplies for U.S. and NATO forces in Afghanistan.