At the same time, General Bantz Craddock predicted that US forces will be in Afghanistan for "at least" a decade, and likely have a presence there for decades to come.

His grim assessment comes as Obama prepares to shift the focus of US military operations to Afghanistan from Iraq to stem an insurgency that has rebounded over the past two years.

Craddock said that, although European allies were expecting Obama to ask them to do more, "I think it's going to be harder for them to do it because of decreasing defense budgets."

He said NATO has plans for replacing Dutch forces in southern Afghanistan in 2010 and the Canadians in 2011.

"The unknown is who else is going to pull out quickly. We don't know that. It's like in Iraq, when nations pulled out without telling anyone ahead time; it's a terrible situation," he told reporters.

The United States has committed to sending an additional 30,000 US troops to Afghanistan, nearly doubling US force levels there from 32,000 troops currently.

But the pace of the US build-up has been slowed by continuing military requirements in Iraq, where there are still more than 140,000 troops and where commanders insist that conditions remain fragile.

Foreign forces needed for at least another three years

In Afghanistan, the NATO-led International Security Assistance Force (ISAF) has about 50,000 troops, which includes 14,000 US troops.

Craddock said it will be another three years before the shortfall in security requirements there can be filled by the Afghan army, and so more foreign forces will be needed to provide security.

"We have to be able to implement our strategy: one, clear out the insurgency; two, hold; three, build," he said.

However, he said that after clearing, "we don't have enough to hold to allow the build."

Asked whether Afghanistan will require a 10-year US military commitment, he said, "At least."

"Maybe not at current force levels but I think we'll see a presence there for decades," he added.

Drug trade fueling insurgency, says NATO general

The greatest security challenge is in southern Afghanistan, where ISAF faces a "very coherent Pashtun insurgency" fueled by the trade in drugs from Afghan poppies, Craddock said.

He said the United Nations estimates that insurgents are now getting $200 - $500 million a year from the drug trade, a big jump from the previous UN estimate of $60 - $100 million a year.

"The uptick in IEDs, the uptick in suicide bombs, the new numbers we're seeing would tell me it has to be paid for," he said, adding that he believes insurgent financing from drugs has at least doubled over the past year to 18 months.

Craddock has pushed for, and obtained, authority for ISAF to attack drug labs as a way of combating the insurgency.

"The question I'm asked all the time is, 'are you losing?'," he said. "No. We're not winning fast enough."

He said European allies have not questioned the requirement for more forces in Afghanistan, but are constrained by declining defense budgets, and that is likely to get worse in current financial climate.

Currently, only six of 36 NATO members meet the alliance's minimum goal of dedicating two percent of GDP to security, he said.

Of those, half have declining defense budgets, he said.

"Absent this financial crisis, still we're challenged. With this financial crisis, we're challenged ever more greatly," he said.

NATO's own advancement hit by crisis

Besides troop contributions to NATO operations, tight budgets also are undercutting efforts to modernize NATO forces and acquire helicopters, drones and other systems needed in Afghanistan, he said.

"So I think we are going to have some hard times ahead. It's going to impact, one, the ability of nations to stay in operations, which is probably the most expensive. Two, it may slow down their transformation," he said.