LONDON — Defence Minister John McCallum challenged his NATO counterparts Wednesday to find a replacement force for Canada's troops in Afghanistan when their mission ends in August after noticing little movement among other members of the alliance to take over.

"We still do not know who will take over from the Canadian forces after we will have completed our one-year commitment at the end of August 2004," he told the Royal Institute of International Affairs. "This should not be the case."

McCallum said that after next August, Canada will not be able to keep as many troops on the ground in Afghanistan as it has now. The Canadian military is committed to two six-month rotations of 2,000 troops in the capital of Kabul, where they work as a stabilization force.

"This is a substantial contribution and our position from the beginning was that this was not a contribution forever, it was a one-year contribution and that NATO has a responsibility to replace us after that year is over," he said later.

McCallum wouldn't rule out a more modest role for Canada after August, but he said the final details of Canada's involvement will have to be determined by Paul Martin's new government after it takes power Dec. 12 from Prime Minister Jean Chretien.

"The new government will consider options, the new government may decide to stay in Afghanistan in a reduced form in one way or the other," he said.

"We would be very hard pressed to maintain numbers at the current level, we could have a contribution that is substantially smaller, but whether we do that and the nature of that contribution will be a matter for the new government to decide."

McCallum was in London after visiting Canadian soldiers in Kabul last week and attending meetings at NATO headquarters in Brussels earlier this week.

He said there was general agreement at NATO to a Canadian suggestion that as many as two to three countries should be lined up to take over in Afghanistan in advance, which he believes would encourage more members of the military alliance to play a role.

"Countries that are members of NATO, I'm hoping they will step up to the plate in Afghanistan," he said.

"If we could get a series of rotations guaranteed for the future, then more countries, whether European or otherwise, would be willing to do it because they would be assured that once their defined contribution is over they indeed can leave." With a number of military missions underway in the war on terror in Afghanistan and Iraq, McCallum said many countries are finding it difficult to deploy more soldiers.

"The general problem is that demands are being made on countries for operations of different kinds in different areas and many countries feel they are pressed," he added.

McCallum said NATO members must find a way of deploying greater percentages of their armies overseas, arguing that Canada has 14 per cent of its army on international missions, second only to the United States among members of the alliance.

Canada is not alone in trying to find relief for its troops stationed overseas, said McCallum, who pointed out that Germany is facing a similar problem at the airport in Kabul, where it is having "great difficulty in finding a nation to replace them."