Harper was to tell Parliament what military contribution his government is prepared to provide in the fight against the al-Qaida splinter group known as the Islamic State of Iraq and the Levant, a spokesman for the prime minister said Thursday night.
"Specifically, his statement will outline Canada’s military contribution to the counter-terrorism operation, as well as our ongoing humanitarian support," Jason MacDonald said in an email.
"A motion will also be put on notice tomorrow and we expect debate and a vote on Monday."
Jason Kenney, one of the most senior Conservative cabinet ministers and an oft-mentioned possible successor to Harper, said earlier on Thursday the government is acting out of an obligation to protect people facing imminent peril.
"There's a consensus in the majority of western democracies, including the United Kingdom, France, United States, from right to left, that we must support the principle of the responsibility to protect,'' Kenney said.
"I hope that 100 per cent of parliamentarians in Canada will say that it's an obligation of Canada as protector of human rights to act to protect people from genocide."
Though parliamentary approval isn't necessary to send soldiers into combat or to participate in airstrikes, Harper indicated the matter will be subject to both a debate and a vote in the House.
NDP Leader Tom Mulcair said the government has been murky at best in disclosing the truth about Canada's current contribution of special forces "advisers," a mission with a 30-day window that's set to close on Saturday. As a result, he said, it's hard to trust what Harper says about the next steps.
"It would interesting to hear some straight answers from the Conservatives," Mulcair said. "A lot of what they've been telling Canadians has been duplicitous on things that are easily verifiable."
It wasn't until earlier this week the government specified that of the 69 special-forces members committed to the operation, only 26 are currently there.
It is believed that what Harper will propose next will be a contribution of fighter aircraft to join the U.S.-led bombing campaign against ISIL.
Mulcair didn't entirely rule out the NDP backing such a plan.
Asked repeatedly Thursday about whether the party would support the mission, he noted that the party had endorsed the first tranche of Canada's military mission in Libya in 2011 when it was based on a UN resolution.
And he said when Canada sent military support to Mali to stabilize the country following a coup, Harper even briefed him.
This time, it's different, Mulcair said.
"We're in a situation that is more political than anything else. We're in a year before an election and the normal rules of the game — openness, frankness, the right attitude with adversaries — isn't there."
Kenney told an anecdote about a Christian community leader in Iraq who described the plight of the elderly and infirm who were unable to flee the encroaching militants in Mosul.
"He said that the jihadists of the Islamic State went to the hospitals and they threatened the elderly with decapitation in their beds," an emotional Kenney said.
"Frankly, when I think of that, I don't think about politics in Canada. For me, it's the humanitarian issue of our generation and we have to act, in my opinion."
Though the Liberals say they, too, haven't made up their minds, Leader Justin Trudeau says his inclination is that Canada should stick to humanitarian aid.
While he acknowledged that Canada has a duty to help deal with the "global security threat" posed by ISIL, Trudeau questioned whether deploying "a handful of aging war planes" is the best contribution Canada can make.
"I think Canadians have a lot more in them than that. We can be resourceful and there are significant, substantial, non-combat roles that Canada can play," he said, suggesting Canada could do more to provide strategic airlift, training, medical support and humanitarian aid for the thousands of displaced Iraqis.
Trudeau's message, however, was obscured by an off-colour remark that quickly earned the government's scorn.
"Why aren't we talking more about the kind of humanitarian aid that Canada can and must be engaged in, rather than trying to whip out our CF-18s and show them how big they are?" he asked.
MacDonald called the remark "disrespectful of the Canadian Armed Forces" and said it made light of a serious issue.
Harper first revealed that an enhanced military contribution was under consideration during an interview in New York City last week.
He made the pitch for joining the U.S.-led coalition to both cabinet and caucus this week, where there appears to have been consensus that Canada must act. There's less agreement on what Canada should do and how long the mission should last.
Meanwhile, other U.S. allies already have their aircraft in the skies or ready to roar.
The British air force began hitting ISIL targets on Tuesday, four days after its Parliament authorized involvement.
Turkey's parliament approved a motion Thursday that gives the government new powers to launch military incursions into Syria and Iraq and to allow foreign forces to use its territory for possible operations against the Islamic State group.
— with files from Jennifer Ditchburn and The Associated Press
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Note to readers: This is a corrected story. An earlier version incorrectly reported Kenney as saying "There's a consensus ... we must support the principle of a military response that protects" when in fact he said "...we must support the principle of the responsibility to protect."
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