By Martin Vennard
Uzbekistan ordered Americans to leave a base there
The temporary closure by Pakistan of the Khyber Pass supply route to Nato and US forces in Afghanistan has highlighted the need for other routes.
Pakistani forces are carrying out an operation to clear militant fighters from the area, following increasing attacks on supply convoys.
The focus for new routes is falling on Central Asia to the north.
Around 75%-80% of the supplies for US and allied forces in Afghanistan flow through Pakistan.
But as recent events have shown, convoys using the Khyber Pass are vulnerable to attack by militants.
The search for different options has also been prompted by US plans to increase the number of its troops in Afghanistan by up to 30,000, which would double its presence there.
The US and Nato are looking at using supply lines through Central Asia to deliver fuel, food and other goods to the military mission in Afghanistan.
To the north, Uzbekistan, Tajikistan and Turkmenistan all have road links to Afghanistan, while a currently abandoned rail link with Uzbekistan could possibly be re-opened.
Uzbekistan ordered the Americans to leave a base there in 2005 in a dispute over human rights issues.
But officials say the current plans would not require further US bases in the region. The US already has one in Uzbekistan's neighbour Kyrgyzstan.
Some supplies would be flown in or transported to Central Asia by land, but others would be bought locally, boosting the region's economy.
They would be transported by commercial companies and would not include weapons or munitions.
Russia would also have to be taken into account, not only because it has traditionally seen Central Asia as its back yard, but also because some of the supplies could be taken across its territory.
But such arrangements could leave the international forces more reliant on cooperation with countries with poor human rights records.