Opposition MPs are crying foul over a Conservative government move to hold a vote Wednesday on whether to extend Canada's mission in Afghanistan by two more years.

The Harper government made the motion on Monday.

During Tuesday's question period, NDP Leader Jack Layton asked Harper if he realized that the decision would "render Canada incapable of responding to other situations in the world."

"We understand that a commitment of this magnitude creates some real constraints on our ability elsewhere," Harper replied.

"However, including the situation in Sudan, we do not expect the need for large scale commitments of Canadian troops elsewhere."

Layton asked the PM why he is bringing the motion forth at this time.

"For months the Prime Minister has been saying that there is no need for a vote on Afghanistan because there is no new mission and now we learn that there is to be a vote on the situation in Afghanistan and our involvement," Layton said.

"And by the way does he believe that providing 36 hours of notice for a debate on a two-year commitment of our troops is the proper way to make foreign policy?"

Harper replied by saying that MPs have had five years to establish their position.

Harper has until now brushed off calls for a full-scale debate and vote by legislators on the mission.

Opposition MPs have agreed to a six-hour debate and then a vote on the motion on Wednesday.

"We are having a debate and a vote on Wednesday,'' Mylene Dupere, a spokeswoman for interim Liberal leader Bill Graham, told The Globe and Mail Monday.

Karl Belanger, a spokesman for NDP Leader Jack Layton, also confirmed the government request, which the NDP has agreed to.

"There's been discussion amongst the parties, and the New Democrats are not going to oppose a vote in the House of Commons, because we pushed for a vote," he told The Globe.

Canada has about 2,300 soldiers in Afghanistan, with most stationed at Kandahar Airfield on a mission that is scheduled to end in February 2007.

CTV's Ottawa bureau chief Robert Fife said extending the mission eases any concerns the NATO-led International Security Assistance Force (ISAF) -- which is taking over the U.S.-led mission in perilous southern Afghanistan -- may have over Canada's commitment.

"They want some certainty from Canada," he said Monday.

"More importantly, it's about politics. The Conservatives are worried about the Liberal leadership race; they're afraid that the next leader may pull the plug on Liberal support for Afghanistan, so they want to get it over now."

Fife said the issue of extending the mission had been discussed in the backrooms on Parliament Hill for the past few days.

However, Col. Michel Drapeau, former director general for the Department of National Defence, said he "fundamentally disagreed" with an extension of the mission.

"I don't think we have the capability to sustain such a deployment and if we do, we're mobilizing everything we have," he told CTV's Canada AM from Montreal on Tuesday.

"That means we don't have the ability to respond to any other emergency mission, be it in Canada or overseas."

Opposition parties have been calling on the government recently to move troops from Afghanistan to Darfur, Sudan, where a bloody internal conflict has led to what many describe as the 21st century's first genocide.

Public support

The Conservative government motion comes at a time when recent public opinion polls show that support for the mission has dropped.

Both Prime Minister Stephen Harper and Foreign Affairs Minister Peter MacKay have travelled to Afghanistan recently to visit Canadian troops in an effort to boost morale and support.

MacKay hinted recently that the mission might be longer than planned.

"The commitment is to finish the job. The commitment is not defined in terms of years -- it's defined in terms of success," he told reporters last week during a visit to Kandahar.

Fifteen Canadian soldiers and one Canadian diplomat have been killed in Afghanistan since 2002.