Bloc Quebecois Leader Gilles Duceppe has threatened to take down Stephen Harper's Conservative government in the fall, if the prime minister doesn't make a firm commitment to pull Canadian troops from Afghanistan by February 2009.

Harper has already implied he will not extend the mission beyond 2009 unless he has a consensus from the other parties.

But Duceppe said Thursday he wants an emergency debate on Canada's role in the Afghanistan once parliament resumes on Sept. 17.

His comments came one day after two soldiers from a Quebec regiment were killed by a roadside bomb in Afghanistan. The body of fallen soldier Pte. Simon Longtin also returned to Canada on Wednesday.

Meanwhile, Liberal Opposition Leader Stephane Dion agreed that Harper should give NATO a firm statement on pulling troops from Afghanistan by February, but said he would not make "threats" like Duceppe.

"Everybody knows there's a possibility of a ... confidence vote where the government can be defeated," he told reporters at a news conference Thursday. "I'm not saying today that's what I want."

Dion added that he would like to wait and see what the government proposes in its throne speech, expected in the fall.

The Afghan mission has been under intense scrutiny this week -- especially in Quebec where support is typically low -- as the number of Canadian casualties in the military continued to increase.

"These latest victims in the Afghan conflict remind us of the dangers and the difficult conditions under which soldiers working in the theatre of war are exposed," said Duceppe.

More than 600 Quebec residents were polled for their views on the Afghan mission just before Longtin was killed and then again right after.

The survey showed the approval rating for the war dropped from 35 per cent before Longtin's death to 28 per cent.

In the first survey, 57 per cent said they disagreed with sending the Van Doos to Afghanistan. After the news of Longtin's death, that number jumped to 68 per cent.

Canada currently has more than 2,300 soldiers in Afghanistan with more than 1,100 from Quebec's Royal 22nd regiment.