The Conservatives pushed back against the government's plan to take on a peacekeeping mission Monday as MPs returned to the House of Commons, accusing Prime Minister Justin Trudeau of treating the military as pawns in a bid for a seat on the UN Security Council.

It didn't take long to prompt a reaction from the Liberals, who said in question period that they’re open to a debate on any peacekeeping mission.

"We welcome a healthy debate both in the House and with Canadians," Defence Minister Harjit Sajjan said in response to questions by interim Conservative Leader Rona Ambrose.

Ambrose stepped up her criticism of Trudeau over the lack of information about a possible peace operation and the risk to the Canadian Armed Forces.

Last week, in an interview with The Canadian Press, Ambrose suggested Trudeau committed to a new, still-undetermined military mission in order to win Canada a seat on the UN Security Council.

On Monday she intensified her argument.

"We know that he wants a seat at the Security Council. We know he has this goal," Ambrose said at a press conference in Ottawa.

"I question his motivation and I don't like this notion that he would use our men and women as pawns on his chess board to figure out what's the fastest way to a security council seat. I don't think that, at the end of the day, it can be at all costs. It has to be in our national interest and it has to make sense for our country."

A source with knowledge of the discussions said the Liberals moved to recommit to peacekeeping prior to deciding to pursue a seat on the UN Security Council. The commitment to peacekeeping is set out in the party's election platform, where there is no mention of pursuing a seat on the Security Council.

Ambrose said the deployment will be dangerous, and decried the lack of information.

"Do we know where they're going? Why they're going? Is this the only option for us, for him? We're not seeing any information, there's no transparency."

Up to 600 troops committed

Last month, Defence Minister Harjit Sajjan travelled to the Democratic Republic of Congo, Tanzania, Uganda, Kenya and Ethiopia on a fact-finding mission "to inform Canada's re-engagement in peace operations," according to a government news release at the time.

The Liberals haven't said where Canada's 600 troops will be deployed. The troop commitment includes engineering and medical units, as well as equipment including helicopters, Sajjan said when the government announced the plan. The government also pledged $450 million over three years for peace and stability projects.

Much of the rest of the world announced its peacekeeping commitments a year ago, at a leaders' summit following the UN General Assembly. Countries including the U.S. and U.K. pledged 40,000 troops and police, as well as "critical enablers" like engineers, field hospitals, helicopters and naval units. The meeting took place during the Canadian election campaign, and no elected representative attended the General Assembly. A spokeswoman for Global Affairs Canada said Canada was only an observer at the peacekeeping leaders' summit.

While the House of Commons resumed sitting on Monday, Trudeau was in New York City to attend the UN General Assembly and related meetings, where he is discussing refugees and economic growth. He's also likely to talk about Canada's peacekeeping pledge.

The Senate defence committee also launched three days of intensive meetings on Monday, focused on peacekeeping as part of its review of Canada's defence policies. The first witnesses have extensive military experience and advised senators to set realistic expectations.

"Any proclamations of objectives have often been unassociated with the reality of achieving them," said retired Lieut. Gen. Mike Day, a former special forces commander. For example, he said, the Canadian Armed Forces can't bring to a struggling country the same level of democracy and security that we have.

"What we can do is immeasurably improve a nation’s lot in life and give them breathing space to create their own form of democracy and security," Day said.

'Maybe we can make a difference'

Retired Lieut. Gen. Charles Bouchard, who commanded the NATO mission in Libya, said the military is part of the solution, not the full solution.

"It's important we understand that when we look at the entire approach, military plays a role but also there's a political aspect, electoral reform, constitutional reform and so on [that] must follow as well," Bouchard told the committee.

Both commanders prepared senators for the reality of another military mission and the likelihood of errors.

Pressed for an example where all elements of a mission -- military, political and diplomatic -- had worked well together, Bouchard said he wasn't aware of it happening.

"I don't have an example," he said. "But we've learned from the past enough to make sure that we can create an example of the next opportunity. Perhaps."

Day said Canada's sometimes tragic and rocky history with peacekeeping should inform the scope of the challenge.

"The reality is we could pack up all our toys and go home, but the fact is, it's not going to make a difference. It's not going to make the world better," he said. "The reality is doing nothing, the world will get worse. Maybe we can keep it on a level playing field. Maybe we can make a difference."

"Look, we're going to stumble. It's not going to be perfect. There will be failure... but I would think less of us if we decided not to engage as a result."