Extending Canada's military mission in Iraq is a matter of "moral clarity" that all political parties should support, Foreign Affairs Minister Rob Nicholson says. In a carefully crafted speech to foreign diplomats on Thursday, Mr. Nicholson‎ set out the Conservative government's case for boosting Canada's role in the U.S.-led coalition. He argued that Islamic State extremists present a danger to the region and a direct threat to Canada and its allies that could grow quickly if it's left unchecked.

Mr. Nicholson's comments lay the groundwork for the government's proposal to the House of Commons next week, when Prime Minister Stephen Harper will ask MPs to support a plan to expand and extend the current six-month mission. The pre-emptive speech, aimed at about 50 foreign diplomats and delivered before a group of journalists, sought to place pressure on federal opposition parties, who have questioned the scope of Canada's involvement.

It was the latest salvo in an extended campaign that saw federal ministers hint repeatedly at plans to renew the military commitment. Mr. Harper said Wednesday that he would seek approval for the extension, a revelation that came in the middle of a break week on Parliament Hill, at a time when many MPs had returned to their ridings.

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That offered the government more space to frame the upcoming debate before facing the opposition in the House of Commons.

Speaking to the diplomats on Thursday, Mr. Nicholson said the Prime Minister would ask all political parties to "come together as Canadians" and support the extended mission.

"He will ask them to support our government's operation to degrade and destabilize this gang of thugs, and in doing so, strip ISIL [Islamic State of Iraq and the Levant] of its power to threaten the security of the region or to launch terrorist operations in Canada," Mr. Nicholson said.

The opposition NDP and Liberal Party both voted against the combat mission in the House of Commons last fall, saying Ottawa should do more to improve humanitarian aid and support refugees fleeing the brutal conflict.

In his speech, Mr. Nicholson argued that both aid and military intervention are necessary in the region, pointing to the plight of Iraq's Yazidi minority as an example. Last fall, tens of thousands of Yazidis were stranded on a mountaintop after fleeing Islamic State attacks in northern Iraq.

"They needed aid, for a catastrophe was in the making," Mr. Nicholson said. "But even before they could receive aid, they needed protection. The two go hand in hand."

NDP Leader Tom Mulcair said earlier this week that he opposes any involvement of Canadian troops in the war against Islamic State militants. There are other places in the world that Canada can help people in need, he said, adding, "We have an absolute freedom to stay out of this and that's what we should be doing."

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Liberal defence critic Joyce Murray said Canada has a role to play in the anti-Islamic State fight, but argued that Mr. Harper has not portrayed the Canadian Forces' mandate honestly.

As the end of Canada's six-month commitment approaches, Ottawa has faced growing calls to clarify the scope of the current military mission in Iraq. Earlier this month, a Canadian soldier was shot and killed by a member of the security forces he was in Iraq to train, prompting additional questions about the proximity of Canadian troops to the front lines of the war.

Canada's military contribution to the battle against IS militants in Iraq currently includes six fighter planes, two surveillance aircraft and an aerial refuelling tanker. In addition, close to 70 Canadian soldiers are assisting Iraqi security forces on the ground in northern Iraq.

However, Mr. Harper's reference this week to expanding – and not simply extending – the mission raises the prospect of a new push for Canada into neighbouring Syria, where Islamic State militants still control vast swaths of territory and a brutal civil war is under way. While the U.S. and some Persian Gulf states have attacked targets in Syria, Canada has so far limited its fighter jets to Iraq.

Mr. Nicholson did not comment on whether next week's proposal will include a new role for Canada in Syria, and he did not discuss the length of the extension the government will seek.