Media playback is unsupported on your device Media caption Natalia Antelava joins a mission to refuel a fighter jet over Afghanistan

Pakistan's decision to shut down Nato supply routes going through its territory means that for the coalition the only remaining overland route to Afghanistan is through Central Asia.

The US military is now preparing to shift more traffic along the roads, rail and air routes that run between the Baltic Sea and Afghanistan via the Caucasus and Central Asia - the so-called Northern Distribution Network.

These routes have been crucial in supplying coalition soldiers in Afghanistan since the war began in 2001.

But in recent months, as Washington's relationship with Pakistan has deteriorated, there has been a steady increase not just of cargo but also diplomatic traffic to secure the support of Central Asian leaders who guard the precious access routes to Afghanistan.

Manas provides proximity. From here the international effort can be sourced much quicker than from any other location in the world Col James Jakobson, Manas Transit Center

But the way through the post-Soviet Stans - as the Central Asian republics are known - is fraught with difficulty and controversy.

Huge blow

In Kyrgyzstan, the newly elected leader Almazbek Atambayev says he wants to shut down Manas air base just outside the capital Bishkek because he sees it as a threat to Kyrgyz security.

"What if America goes to war with Iran and next thing we know Tehran will be bombing Manas," he said in a BBC interview shortly after his election in October.

Mr Atambayev said his decision not to extend the lease when it runs out in 2014 was non-negotiable, and that the US should respect the agreements it signed.

In the past, the US has played down similar statements from Mr Atambayev's predecessors, saying there were alternatives for a similar base elsewhere.

And, anyway, US President Barack Obama hopes to get combat troops out of Afghanistan by 2014.

But many experts say the closure of the base would be a huge blow for the US, especially at the time it is withdrawing.

Image caption Virtually every Nato soldier passes through Central Asia

Virtually every Nato soldier passes through Central Asia and on any given day there are some 2,000 troops coming through Manas, either on their way to Afghanistan or on their way home. The base is also used for refuelling fighter jets and bombers in Afghanistan.

"It takes only two hours to get from here to Kabul," says Col James Jakobson, who is in charge of the Manas Transit Center.

"So Manas provides proximity. From here the international effort can be sourced much quicker than from any other location in the world."

With the future of the base uncertain and routes via Pakistan unreliable, the US has also been courting other Central Asian leaders.

In the same week as the White House was congratulating Libyans on the death of Col Muammar Gaddafi, Hillary Clinton stood in front of the cameras in Tashkent shaking hands with a man whose human rights record is often compared to the former Libyan leader.

"I wanted to come to Tashkent, to see you and to see your people," she said, smiling broadly at Uzbekistan President Islam Karimov, who nodded approvingly.

"He is the biggest beneficiary of the troubles between the US and Pakistan and he can't believe his luck," said a Tashkent-based journalist, who did not want to be named for his personal safety.

"This will benefit him enormously - both politically and financially and it's bad news for whatever is left of civil society here."

'Scared of 2014'

Stern, short and stocky, Mr Karimov may not have the flamboyance of the late Libyan leader and, unlike Libya, his country has never been on the radar of the Western media or its public.

The Obama administration is clearly scared as 2014 is approaching Paul Quinn-Judge, International Crisis Group

But there is, observers say, plenty of room for comparison.

"When it comes to human rights abuses, lack of freedom and a complete intolerance of dissent, Mr Karimov is right up there with some of the most brutal of Arab dictators," says Paul Quinn-Judge, Central Asia Director for the International Crisis Group.

But this autumn the US Congress lifted its ban on military aid to the Uzbek regime, seven years after imposing the measures because of widespread human rights abuses.

Rights groups accuse the US of empowering one of the world's most brutal regimes.

"The Obama administration is clearly scared as 2014 is approaching and they don't only need to get the troops in and out of Afghanistan, they'll need to get a lot of expensive equipment out," says Mr Quinn-Judge.

"But this is foreign policy reduced to problem solving. The problem is Afghanistan, the solution is seen to lie with Islam Karimov."

Mr Obama's priority is to end the war and get the troops home.

But paving routes out of Afghanistan is a challenge, and many fear that the deals Washington makes along the way could have a lasting impact on the whole region.