They said Parliament would hold a six-hour debate on the matter starting at 3 p.m. (1900 GMT) on Wednesday and then stage a vote. When contacted by Reuters, the chief spokeswoman for Prime Minister Stephen Harper declined to comment.

"They want a two-year extension to the mission," said a spokesman for Bill Graham, leader of the official opposition Liberal Party.

Canada's troops, based in the southern Afghan city of Kandahar, were supposed to return home in February 2007. Four soldiers died in a roadside bomb blast on April 22, bringing to 16 the number of Canadians who have died in Afghanistan since the September 11 attacks.

The deaths sparked calls for a parliamentary debate on what Canada is doing in Afghanistan, something which Harper, who took office in January, has refused to do, saying it would only undermine the troops' morale.

An Ekos poll provided to Reuters last week showed support among Canadians for the mission in Afghanistan had slipped but was still relatively solid despite the latest casualties.