James Jones, the top Nato commander in Europe and a US Marine general, said he wanted about 2,000 to 2,500 more alliance troops to expand the roughly 18,500 troops currently deployed in Afghanistan, as well as attack helicopters and transport aircrafts.
After a three day visit to Afghanistan, Jones said on Thursday that some of the 26 nation that make up the alliance have not contributed enough resources, but he did not single out any.
Jaap de Hoop Scheffer, Nato's secretary general, also urged alliance members to come to the support of the British, Canadian and Dutch troops leading the fight against the Taliban guerrillas in the south.
"Those allies who perhaps are doing less in Afghanistan should think: Shouldn't we do more? There are certainly a number of allies who can do more," Scheffer said on Thursday, while in Brussels.
Diplomats say Germany, which leads the Nato mission in the relatively calm north, is under pressure to offer reinforcements for the south, but a German defence spokesman played down prospects of Berlin redeploying any of its 2,700 troops southward, saying: "It is still the case that our focus is on the northern region."
Since the alliance extended its peacekeeping mission to southern Afghanistan a month ago 21 Nato soldiers have been killed and 37 injured in fierce fighting with the Taliban.
"We are talking about modest reinforcements," Jones told an earlier news briefing at NATO's European military headquarters in Mons.
Jones said he would urge national military chiefs meeting in Warsaw on Friday to study possible reinforcements and remove restrictions, known as caveats, on how and where their country's troops can be used.
Nato spokesman James Appathurai acknowledged the alliance had underestimated both Taliban numbers and tactical strength.
In an attempt to bolster its operation in Afghanistan, the US Senate has approved a $470 billion defence bill, which includes $63 billion in emergency funds for its operations Iraq and Afghanistan.
The bill also provides a 2.2 per cent pay raise for all military personnel Iraq and Afghanistan.
An additional $200 million would fund an intelligence unit to hunt top al-Qaeda’s Osama bin Laden.
The measure also requires the US Defence department to report to congress every three months about progress made toward catching Bin Laden.
The defence spending bill also approved $700 million to bolster Washington's efforts to fight Afghanistan's flourishing cultivation of poppy, the plant from which heroin is derived.