Members of the Canadian Forces are already headed to the Middle East to prepare for the deployment of 600 military personnel as part of the government's newly announced combat mission against Islamic State extremists in Iraq, sources say.

The full deployment will be the subject of a debate in the House of Commons on Monday, with the Conservative Party set to use its majority to win a vote in the face of Liberal and NDP opposition.

The mission, however, is under way. A senior government official said a small "reconnaissance team" has started preparations for the arrival of six CF-18s and other military aircraft at a staging base at an undisclosed location. "The advance team is less than a dozen, focused on co-ordinating basing and logistical details with allies for the purpose of deploying the assets committed Friday by the Prime Minister," a senior government official said.

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The Harper government will also focus this week on beefing up its case to Canadians for the military mission, after facing criticism that it has failed to justify the need for a six-month campaign of air strikes in Iraq and, potentially, Syria.

On Wednesday, Public Safety Minister Steven Blaney will be flanked by the heads of the RCMP and CSIS at the House Committee on Public Safety, where they will discuss the domestic threats of homegrown terrorism, as well as the government's plans to crack down on Canadian IS supporters.

More than 100 Canadians have gone abroad to fight against Western forces, but an estimated 80 have returned, the official said.

Mr. Blaney, RCMP Commissioner Bob Paulson and CSIS director Michel Coulombe "will lay out the threats to Canadians posed by terrorist groups and domestic radicals," the official said, adding the government is not planning to announce new measures, but will offer a sense of its priorities for action.

Prime Minister Stephen Harper announced plans to go to war on Friday, saying that Canada will send six CF-18 fighters, a refuelling aircraft and two surveillance planes to participate in an international coalition. The plan rules out the use of Canadian ground troops, but it also extends the current deployment of 26 military advisers to northern Iraq for an additional six months.

The deployment will be the subject of a day-long debate in the House on Monday, with the Conservative Party putting up Defence Minister Rob Nicholson and Foreign Affairs Minister John Baird to speak in favour of the mission, among others.

NDP Leader Thomas Mulcair and Liberal MP Marc Garneau will launch the debate for their respective sides, attacking the government's for failing to achieve a consensus on the need for the mission.

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NDP MP and foreign affairs critic Paul Dewar said he is worried that the government is open to conducting bombing missions in Syria if it has the approval of the regime of Syrian President Bashar al-Assad.

He added that the government's promise of a six-month deployment, open to renewal, raises questions about the duration of Canada's involvement in the conflict.

"We have to nail down what this all means," he said in an interview on Sunday. "We're all morally outraged about what is happening [in Iraq and Syria], but that's not a strategy."

Announcing the mission last week, Mr. Harper said Canada must protect itself from a jihadi group that has threatened this country and its allies, and also has a moral obligation to degrade the Islamic State's capacity to commit atrocities against the people in Iraq and Syria.

"It has tortured and beheaded children. It has raped and sold women into slavery. It has slaughtered minorities, captured prisoners and innocent civilians … whose only crime is being or thinking differently," Mr. Harper said.

Liberal Leader Justin Trudeau has called for a mission centred on humanitarian aid, raising questions about the ability of Canada's "aging warplanes" to have any impact in the ongoing conflict.