Even after an extra US Army brigade joins the fight against Afghan insurgents next January, three times as many reinforcements will be needed soon after, the highest-ranking US general in Afghanistan has said.
Commander of NATO-led international forces in the country General David McKiernan told reporters travelling with US Defence Secretary Robert Gates that the war was being fought with insufficient resources.
If more troops were not forthcoming, the fighting would last longer and take a higher toll, he said.
His comments came as four soldiers serving in the US-led coalition in Afghanistan were killed when their vehicle struck a roadside bombin the east of the country, the force said.
An Afghan national was also killed by the improvised device in the province of Paktia, which came as Dr Gates was in Afghanistan for talks with President Hamid Karzai.
The nationality of the soldiers was not given, but most of the troops deployed in that part of the country are from the United States.
It was not immediately confirmed who was behind the bomb blast but Taliban militants waging an increasingly bloody insurgency have been using improvised bombs against foreign troops.
Dr Gates was in Kabul to discuss the growing unrest with Mr Karzai. General McKiernan said on Tuesday that he needed more than 10,000 extra troops to fight the insurgency.
The hard-line Islamic Taliban, ousted from power in late 2001 in a US-led invasion, are trying to topple the Western-backed Government and force out the tens of thousands of international troops supporting it.
Their insurgency includes suicide attacks, roadside bombings and attacks on Afghan and foreign military targets, and is at its worst in the south and east of Afghanistan.
There are about 70,000 international soldiers in Afghanistan. Most operate under the command of the NATO-led International Security Assistance Force but there is also a separate US-led coalition.
General McKiernan disputed the notion that the US and NATO war strategy had failed and needed to be overhauled.
''Our strategy of approaching counter-insurgency operations is a valid strategy here,'' he said.
''Our problem is we don't have enough resources to do it with.''
The general added that he was referring not only to insufficient military forces but also short-comings in Afghan governance and a shortage of international economic aid.
General McKiernan spoke before meeting privately with Dr Gates, who was making his first visit to Afghanistan since December.
The general said the army brigade arriving in January would fill an urgent short-term need based on an assessment that fighting in eastern Afghanistan was tougher than believed six months ago.
''There are an additional three brigade combat teams'' that have been validated by the Pentagon as a requirement.
He would not say exactly how many extra soldiers that entailed, but said it was more than 10,000.
General McKiernan was asked what the consequence would be of not getting the three combat brigades he believed were needed in 2009 beyond the one US President George W. Bush is sending in January.
''The danger is that we'll be here longer and we'll expend more resources and experience more human suffering than if we had more resources placed against this campaign sooner,'' he said.
Dr Gates arrived in the Afghan capital after presiding at a ceremony in Baghdad where General Ray Odierno took over for General David Petraeus as the top US commander in Iraq. AP, AFP