After more than 11 years of US-led military intervention in Afghanistan, the two countries are hammering out a deal to allow a limited US troop presence to remain after the international coalition leaves next year.

The size of the "residual" force has not been agreed, with numbers ranging from 2,500 to 12,000, according to US officials, as Washington winds down a war that has become deeply unpopular at home.

Soldiers kept in Afghanistan would target Al-Qaeda militants and help train the local army and police -- but a hasty withdrawal could also threaten fragile gains secured since the Taliban were ousted in 2001.

"We are in very serious and delicate negotiations with America," Karzai said. "America has got its demands, Afghanistan too has its own demands, and its own interests... They want nine bases across Afghanistan.

"Our conditions are that the US intensify efforts in the peace process, strengthen Afghanistan's security forces, provide concrete support to the economy -- power, roads and dams -- and provide assistance in governance.

"If these are met, we are ready to sign the security pact," he told the audience during a speech at Kabul University.

US officials have reportedly said that if 6,000 troops were kept in Afghanistan after 2014, only two bases, in Kabul and at Bagram airfield, would be maintained.