U.S. Defence Secretary Robert Gates has endorsed an Afghan government proposal to increase the size of its army by more than 50,000 troops.

The new plan will cost well over $10 billion US. Pentagon press secretary Geoff Morrell said Thursday officials are currently looking at ways to finance it. Options would include seeking money from NATO allies.

Morrell said the proposal would increase the size of the Afghan army from a planned 80,000 troops to roughly 122,000, plus 13,000 in support staff.

In addition, Gates is expected to approve a plan that would give U.S. Army Gen. David McKiernan broader control over U.S. forces in Afghanistan. Currently, McKiernan commands the NATO-led coalition in Afghanistan, which includes about 15,000 U.S. forces.

Under the new proposal, McKiernan also would control the additional U.S. forces in Afghanistan who are training the Afghan army and police. There are about 33,000 U.S. troops in Afghanistan, the highest since the war began.

All told, the five-year plan could cost about $20 billion US, said the New York Times, which reported the proposal on it website late Thursday.

Attacks from Taliban militants have spiked in recent months in Afghanistan, and commanders have said repeatedly they need additional U.S. forces. Commanders have asked for three additional combat brigades, and military officials hope that as troops levels are reduced in Iraq they will be able to shift forces to Afghanistan by early next year.

The Pentagon long has been considering military commanders' suggestions to better co-ordinate the mission in Afghanistan.

Plan still needs approval

The plan, which does not yet have final approval, would leave the smaller number of U.S. forces who are battling the Taliban and overseeing detainees under the control of U.S. Central Command. Currently, U.S. Central Command also directs the training forces.

Morrell said the proposal would not blend the NATO and training missions.

He added this "imminent" decision has come after close consultation with leaders of the NATO allies.

The move to add to McKiernan's authority is designed to extend U.S. control of forces into the country's volatile south, an idea partly linked to an expectation of a fresh infusion of U.S. combat troops in the south next year.

Taliban resistance has stiffened in the south since NATO took command in mid-2006, and some in the U.S. administration believe the fight against the Taliban could be strengthened if the United States, whose span of control is now limited to eastern Afghanistan, were also in charge in part or all of the south.

Giving the United States more control in the south would address one problem cited by U.S. officials: the NATO allies' practice of rotating commanders every nine months — and their fighting units every six months, in some cases. In the U.S. view, nine-month commands are too short to maximize effectiveness.

Changing the command structure to give a U.S. general more control in the south would, in effect, mark a partial "re-Americanization" of the combat mission. That could be politically controversial, given U.S. interests in maintaining close ties with NATO in fighting terrorism.