KABUL - The United States has pledged $16 billion (10 billion pounds) to spend on training and equipping Afghanistan's army and air force, but the country needs more to build a force that can guarantee stability, an Afghan army official said on Wednesday.

Defence Ministry spokesman Zaher Azimy said Kabul hoped a donor conference in London next month would provide cash and supplies needed for ambitious plans to expand the army to 240,000 soldiers, from over 100,000 at present.

For the expansion process of the army, the United States has pledged $16 billion, Azimi said, adding that the cash would be spread out over the period needed to scale up the army, currently estimated at around four years.

This is not enough by any means and we are hopeful to receive more assistance in London conference (from other NATO allies).

He was speaking at a joint news conference with a spokesman for NATO-led forces, who did not dispute the $16 billion figure.

With violence at the highest level in years, U.S. President Barack Obama is sending in 30,000 extra troops to Afghanistan to try to turn the tide. Other NATO countries are sending some 7,000 more.

But Washington's plan also calls for U.S. troop levels to be scaled down from July 2011 as they gradually hand over security to the Afghans and the White House has said the United States will not be in Afghanistan in eight or nine years time.

Part of the U.S. cash is likely to cover planned spending on over 150 aircraft -- including helicopters, and reconnaissance, combat and transport planes -- that are vital for traversing Afghanistan, a rugged country with weak infrastructure.

Other assistance will target extra training and construction of bases as well as providing NATO-standard weapons, Azimy said.
The army is seen as a relative success story both for the Afghan government and its Western allies. Washington has poured $17 billion into building up the forces since the ouster of the Taliban in late 2001, Azimy said.

But it has also faced some problems with desertions in the past and several attacks by Afghans on the foreign troops they serve beside have highlighted sometimes testy relations between the two, prompting public debate in the West about the war.

Last month, an Afghan policeman killed five British soldiers at a military compound in southern Helmand province. The Taliban said he was one of their fighters who had infiltrated the force.

In the latest attack, an Afghan soldier on Tuesday shot dead an American soldier and wounded two Italian troops in a joint Afghan and foreign base in northwestern Badghis province.

Azimy said the assault was a result of a verbal argument between Afghan and foreign soldiers, not a Taliban attack.

A spokesman for the NATO-led force said the incident would not dent trust between Afghan and foreign troops.

Every time the insurgents will try to use one type of incident against us, try to break that partnership, we won't let that happen, Wayne Shanks said. Our forces gain strength by operating beside their Afghan partners and will continue to do that.

(Editing by Emma Graham-Harrison)