BISHKEK (Reuters) - Kyrgyzstan’s parliament voted on Thursday to close the only U.S. air base in Central Asia, removing one of the U.S. military’s supply routes into Afghanistan as it prepares to send more troops.

The United States also faced reluctance from its NATO allies to provide more soldiers to complement the extra 17,000 troops it is sending to Afghanistan to tackle the Taliban insurgency.

Defense Secretary Robert Gates, attending a NATO meeting in Poland, said Washington wanted its allies to send more troops to provide security for a presidential election in Afghanistan in August but acknowledged big increases were unlikely.

Kyrgyzstan’s decision to close the U.S. air base undermined its plans to diversify supply routes into Afghanistan after supply convoys were attacked by militants in Pakistan.

Kyrgyzstan’s parliament backed a decision by President Kurmanbek Bakiyev -- announced in Moscow after he secured a $2 billion package of aid and credit from Russia -- to close the Manas air base 35 km (22 miles) from the capital Bishkek.

Kyrgyz Foreign Minister Kadyrbek Sarbayev said Washington would be given 180 days to wrap up operations after the parliamentary decision was signed into law.

In Washington the Pentagon said it was still looking at what it could offer Kyrgyzstan to keep the base open.

“We continue to consider what we might be able to offer the government but we’re not prepared to stay at any price and we continue to look at other options that are available to us,” Pentagon spokesman Bryan Whitman said.

NATO spokesman James Appathurai said NATO members would continue to supply their forces as needed. “We have full stock piles ... it is an inconvenience for allies and one to regret, but we can certainly absorb it,” he said.

The United States and its allies fly troops and supplies from bases in Europe and the Gulf and could increase this traffic to make up for the loss of Manas air base.

But the closure underlined the challenges Washington faces in enlisting Russian support for its campaign in Afghanistan.

Russia says it is willing to help with the shipment of supplies through former Soviet Central Asian states, but is suspicious of any attempt by Washington to build a permanent military presence there.

A first shipment of non-military goods is expected to leave NATO member Latvia shortly, going through Russia, Kazakhstan and Uzbekistan to Afghanistan.

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HEAVY COMMITMENT

The United States faces a major challenge in Afghanistan, with the Taliban insurgency growing in strength both there and in neighboring Pakistan.

U.S. Army General David McKiernan told reporters in Washington that 2009 would be a tough year, but the extra troops would help break a stalemate in southern Afghanistan.

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But he said it would be a long struggle. “For the next three to four years, I think we’re going to need to stay heavily committed ... in a sustained manner in Afghanistan.”

The reinforcements will take U.S. troop numbers to around 55,000, in addition to the 30,000 troops from 40 other mostly NATO countries already operating in Afghanistan.

Most of the extra troops will be sent to southern Afghanistan where mostly British, Canadian and Dutch troops have not had enough soldiers to keep effective control of ground they have captured from the Taliban.

Gates acknowledged in the Polish city of Krakow that large increases in troops from Washington’s NATO allies were unlikely but said he would also seek more help on civilian development.

“There needs to be a strengthening on the civilian side as we are strengthening on the military side. And frankly I hope it may be easier for our allies to do that than significant troop increases especially for the longer term.”

NATO Secretary-General Jaap de Hoop Scheffer also said NATO needed to stop looking at Afghanistan in isolation and recognize Taliban militants were also fighting to destabilize Pakistan.

“I can say again that I believe the Pakistani government is serious about fighting extremism. What we need in NATO is to stop seeing Afghanistan in isolation and to start seeing it in a more regional approach.”

More than seven years after the U.S.-led invasion of Afghanistan to topple the Taliban following the 9/11 attacks on the United States, the Islamist insurgency has spread from Pakistan’s border with Afghanistan deeper into the country.

Earlier this week, the Pakistan government stuck a peace deal to end fighting between the Taliban and the Pakistan Army in the Swat valley, just 130 km (90 miles) north of Islamabad, by promising to reintroduce Islamic sharia law there.