The Conservative government will defend ordering special forces soldiers to Iraq on both moral and pragmatic grounds, arguing that Canadians are obliged to help stop a savage militant group whose self-proclaimed caliphate risks becoming a training ground for terrorists who could attack Canada and other Western countries.

The Commons hasn't resumed sitting yet, but Foreign Affairs Minister John Baird and Defence Minister Rob Nicholson are appearing before MPs at a special committee hearing Tuesday to argue the case for Canada's surprise decision last week to send dozens of this country's most elite soldiers to northern Iraq.

Prime Minister Stephen Harper is facing pressure to explain why Ottawa is sending soldiers into such a deadly arena, even as military advisers rather than fighters, and to assuage concerns that mission creep will lead to Canada being drawn further in the conflict. The deployment arises not from a collective decision of the North Atlantic Treaty Organization or the United Nations but rather, according to Mr. Harper, a direct request from U.S. President Barack Obama.

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About 70 Canadian special forces soldiers will join the Americans to serve as military advisers to Kurdish forces who are battling the Islamic State militants, formerly known as Islamic State of Iraq and the Levant (ISIL), a group that has cut a swath of suffering across the region and imposed its own harsh brand of Islamic law on territory it has seized.

Right now the Canadian deployment is set for only 30 days, but Mr. Harper and his cabinet are free to renew it as they see fit.

Canadian troops could be on their way as early as this week if Ottawa is able to nail down deployment plans, a government source says.

The Official Opposition NDP says Mr. Harper is out of line and should delay sending soldiers to Iraq until Parliament debates the mission. The Commons resumes sitting next week. "We have the responsibility to ensure the mission is defined and has clear objectives," NDP foreign affairs critic Paul Dewar said.

The Tories plan to argue the militants pose a danger outside of Iraq, as Mr. Harper explained last week at the conclusion of the NATO summit near Cardiff, where he described the region under Islamic State's control as a future source of terrorists who could threaten Canada and other Western allies.

Mr. Baird and Mr. Nicholson will be accompanied by Andrew Bennett, the Conservative-appointed watchdog of international religious freedom, who will outline the persecution of religious minorities and other Muslims by the Islamic State militia.

Adam Hodge, a spokesman for Mr. Baird, said the NDP has the means to stage a debate in the Commons using time allotted to opposition parties.

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"The opposition parties are free to use one of their multiple opposition days to debate the issue," Mr. Hodge said.

"The fanaticism of the ISIL terrorist group is a real threat to regional security and millions of innocent people in Iraq, Syria and beyond. Left unchecked, ISIL is also a direct threat to Canada and its allies."

Mr. Dewar said it's hard to imagine peshmerga Kurdish fighters need advice on combat. He said when he accompanied Mr. Baird to Iraq last week it appeared Iraqis urgently require food, water and blankets to lessen the problems faced by hundreds of thousands of displaced people. "It was very clear they didn't need boots on the ground. They needed help with this humanitarian crisis," Mr. Dewar said.

Mr. Dewar said he believes it will be difficult for Canadian military advisers to stay out of the fray. "This is an asymmetrical war. This isn't a war where you have two fronts and you can stay in the back and tell people how to conduct their business," the NDP MP said.

"Ask Obama about mission creep," Mr. Dewar said, recalling the President's promise to withdraw U.S. troops from Iraq after George W. Bush mired the United States in a lengthy conflict there.

Mr. Harper has already warned this deployment may not be the end of Canadian involvement in Iraq, saying military efforts announced to date by Western countries will not prove sufficient to shut down the Islamic State.

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The militant group has attracted foreigners to join its ranks and fight in Iraq, including Canadians. The Canadian Security Intelligence Service says more than 100 Canadians have left the country to support or participate in a variety of extremist movements abroad.