WASHINGTON - The global financial crisis could force U.S. allies to scale back their efforts in Afghanistan, or possibly even pull out, NATO's top commander said Friday.

"We are going to have some hard times ahead," Supreme Allied Commander Gen. John Craddock said in Washington.

"And it's going to impact, one, the ability of nations to stay in operations -- which is probably the most expensive."

Already, Canada and the Netherlands have signalled they will leave by 2011, Craddock said. That means the United States and other allies will have to cover the costs of securing Afghanistan, which president-elect Barack Obama's administration has called a top priority.

The Netherlands said well before the financial crisis began that it would leave Afghanistan and Canada will have already been there for a decade by 2011.

Craddock predicted troops would need to remain in Afghanistan for "at least" 10 years.

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

An estimated 31,000 U.S. troops currently are in Afghanistan, with between 20,000 and 30,000 more expected over the next year.

Most of the 26 countries that make up the North Atlantic Treaty Organization have been too cash-strapped for some time to meet minimum spending levels each is expected to contribute for security missions.

NATO countries are asked to spend two per cent of their gross domestic product on security issues that Craddock said mostly goes toward military efforts. Only six of the 26 countries are meeting that benchmark, he said.

"Absent this financial crisis, still we were challenged," Craddock said.

"With this financial crisis, we're challenged even more greatly. This is going to be difficult."

He added: "It's going to be harder and harder for nations to continue to support this performance capability that we're asking."

Craddock described an "anxiousness" by European leaders about Obama's plans but said he has not heard European allies suggest the incoming president is moving too quickly or wants too many troops in Afghanistan.

"I think there is some expectation and some anxiousness -- not angst but anxiousness," Craddock said.

"'Where's this going to go? How fast, how far and what will be expected of us?' is what I'm hearing from those nations," he said.