BRUSSELS (AFP) - Afghanistan wants and will sign a key security pact with Washington in "good time" to ensure Nato maintains a training mission after it ends combat operations there next year, an official said Wednesday.

As US and Nato officials warn that Kabul must sign soon or run the risk of losing post-2014 aid, an Afghan foreign ministry spokesman insisted the government "not only desires but also supports signing" the Bilateral Security Agreement.

President Hamid Karzai has refused to sign the BSA, which would set the legal and operational framework for Nato's post-2014 training mission, until elections in April when he stands down.

Karzai also says he wants only Afghan forces to be used in searches of homes to end civilian casualties.

Afghan foreign ministry spokesman Janan Mosazai said his minister had told a Nato meeting that the government had two conditions, the first being the launch of "meaningful peace" talks with the Taliban rebels.

The other is the "complete cessation of any military operations against Afghan homes", Mosazai said.

Afghan "homes are not where the terrorists are," he added, stressing that only local forces should be used in such operations.

Asked about suggestions that Karzai might instead delegate a member of the government to sign the BSA, Mosazai said that the decision rested solely with the president.

As for the possibility of an aid cut-off, Mosazai said "we do not anticipate such a scenario", stressing that both sides shared common interests.

The United States and Nato has a stake in "maintaining a long-term security engagement with Afghanistan", he said.

"We do not look at (aid) as charity but rather as a worthwhile investment in the security" of Afghanistan and the wider region, he added.

US Secretary of State John Kerry repeated at the Nato foreign ministers meeting that Kabul should sign, and soon, to clear the way for implementation and funding of the post-2014 mission.

In 2011, the United States withdrew from Iraq when it failed to secure a similar troop status accord.

About 75,000 Nato combat troops are still deployed in Afghanistan, the majority of them American, and are being steadily drawn down as the alliance prepares to end its longest and biggest ever military operation.

Under the training and advisory mission, up to 12,000 troops, expected to be mostly American, would be based in the country from 2015.