On Tuesday, the US commander for the Middle East and Central Asia, General David Petraeus, held talks in Uzbekistan, which has rail links with Afghanistan.
The US has already reached deals with Russia and Kazakhstan to send non-military cargo to Afghanistan using their rail networks, but the supplies would have to go through Uzbekistan. The US used to have an air base in Uzbekistan that served troops operating in Afghanistan.
But Uzbek authorities closed it in 2005 after criticism from the US and EU over a crackdown on a mass protest in the town of Andijan.