Harper said Canada will join the U.S. and its allied partners for a period of up to six months in launching airstrikes against the Islamic State of Iraq and Syria (also known by the acronyms ISIS and ISIL). He said Canada will also extend the deployment of up to 69 Canadian troops in a non-combat role to advise security forces in Iraq.
The government's motion is slated for debate in the House on Monday before it is put to a vote.
Opposition Leader Tom Mulcair abstained from telling Parliament which way the NDP would vote on the government's motion, but in a subsequent interview airing Saturday on CBC Radio's The House, Mulcair told guest host Chris Hall "we're not going to be supporting Mr. Harper' motion."
Liberal Leader Justin Trudeau told the Commons while there is a role for Canada to play in the fight against Islamic militants, the Liberals would not support the government's motion "to go to war in Iraq."
Green Party Leader Elizabeth May urged the government to spend more than just one day debating the motion.
Here's how Harper outlined the objectives for an expanded Canadian military mission against ISIS, and the opposition party leaders' responses:
"Let me be clear on the objectives of this intervention. We intend to significantly degrade the capabilities of ISIL. Specifically, its ability either to engage in military movements of scale or to operate bases in the open.
"While ISIL will not be eliminated, the risks presented from the territory in which it operates will be significantly reduced to those of other, similar ungoverned spaces in the broader region.
"We will strike ISIL where – and only where – Canada has the clear support of the government of that country. At present, this is only true in Iraq. If it were to become the case in Syria, then we would participate in air strikes against ISIL in that country also.
"Let me assure Canadians that the government is seized with the necessity of avoiding a prolonged 'quagmire' in this part of the world. Indeed, we and our allies are acting now precisely to avoid a situation that was clearly headed to a wider, protracted and much more dangerous conflict. Let me also say that the military measures we are taking do not in any way preclude humanitarian actions. There is no either/or here.
"This is in addition to large-scale financial assistance already being furnished to the significant number of countries in the region that have been impacted by the humanitarian catastrophe in Syria."
"Why is military action supposedly our only choice in Iraq, and not even considered elsewhere?
"ISIS has thrived in Iraq and Syria precisely because those countries lack stable, well-functioning governments capable of maintaining peace and security within their own borders.
"Canada’s first contribution should be to use every diplomatic, humanitarian and financial resource at our disposal to respond to the overwhelming human tragedy unfolding on the ground and strengthen political institutions in both those countries.
"With the well-deserved credibility Canada earned by rejecting the initial ill-advised invasion of Iraq, we are in a position to take on that task.
"The tragedy in Iraq and Syria will not end with another Western-led invasion in that region. It will end by helping the people of Iraq and Syria to build the political, institutional and security capabilities they need to oppose these threats themselves.
"Canada, for our part, should not rush into this war."
"We think there is a role for Canada to be involved in the fight against ISIL, but there is a clear line between non-combat and combat.
"It is much easier to cross that line than to cross back. It is always easier to get into a war than to get out of one.
"The prime minister has a sacred responsibility to be honest and truthful with people, especially about matters of life and death.
"At the end of every decision to enter combat is a brave Canadian in harm’s way. We owe them clarity. We owe them a plan. Most of all, we owe them the truth.
"The prime minister has offered none of those.
"The Liberal Party of Canada can not and will not support this prime minister’s motion to go to war in Iraq."
"We need to sign the arms trade treaty. We need to stem the conventional flow of arms to terrorists. We need to track the money. We need to find out who's fuelling these people. We we need sensible plans. We we need to make sure there are not vast numbers, cohorts of unemployed young men who feel alienated within their societies.
"If this is called practising sociology, consider me guilty of it. I call it thinking.
"I completely support all of the prime minister's intentions. We cannot allow these horrific crimes to go unanswered. But we must make sure that whatever we do, doesn't make matters worse.
"And that's why, Mr. Speaker, I hope we will have a fuller debate. And more than just one day.
"Bombing has never ended an Islamic or any religious extremist terrorist threat. It has, in fact, time after time again made matters worse. Let's try to look at the lessons of history before we go to war again."