U.S. President George W. Bush urged NATO allies on Wednesday to send more troops to Afghanistan, saying the alliance could not afford to lose its battle against Taliban insurgents and al Qaeda militants.

In a keynote speech before a summit of the 26-nation defence alliance in the Romanian capital, Bucharest, Bush said: "As (French) President (Nicolas) Sarkozy put it in London last week, we cannot afford to lose Afghanistan. Whatever the cost, however difficult, we cannot afford it, we must win. I agree completely.

Noting that France and Romania were due to send more troops, he said: "We ask other nations to step forward with additional forces as well."

NATO allies want the Bucharest summit, starting later on Wednesday, to send the message that its 47,000-strong peacekeeping force will stay in Afghanistan for as long as necessary to battle the insurgency.

"Our alliance must maintain its resolve and finish the fight... If we do not defeat the terrorists in Afghanistan, we will face them on our soil," Bush said.

French Prime Minister Francois Fillon said on Tuesday Paris was looking to send several hundred more troops to Afghanistan.

That was far short of the 1,000 extra soldiers that some NATO allies had been expecting and it was not clear whether it would be enough to cover a Canadian demand for reinforcements in the south.

Ottawa has said it could pull its 2,500 troops out of the fight next year if the reinforcements were not forthcoming.