VICTORIA -- It looks good on paper and has a certain nostalgic appeal for left-leaning voters, but the NDP pledge to make Canada once again the top western troop contributor to United Nations peacekeeping comes with a cost -- one a defence expert says the party and its supporters might not be expecting.

Dave Perry, of the Global Affairs Institute, says the plan would require the military to expand, perhaps by as much as 10,000 soldiers -- bringing the total full-time strength to roughly 78,000 -- depending on which other country the party wants to measure Canada against.

"They'll need to build a much bigger army to get us to No. 1," Perry said.

Tom Mulcair, kicking off the last nine days of the campaign on the West Coast, said he's committed to meeting the goal.

"With an NDP government making peace a priority, we'll be back to No. 1 in the world," Mulcair said at a Vancouver Island rally, where he stepped up attacks on both Stephen Harper and Justin Trudeau over the Trans-Pacific Partnership trade deal and the environment.

Reported heavy turnout at advanced polls across the country this weekend buoyed Mulcair, who predicted that voters are in the mood for change and he said he's confident they'll look to the NDP. At the same time, he brushed off a growing number of dismal polls saying the opinion-makers didn't see the party's surge coming in 2011.

The NDP defence policy, released Friday as part of the overall platform, appears crafted to appeal to middle-of-the-road voters without alienating the party's pacifist supporters.

Among the other promises in the policy is a commitment to maintain stable defence funding, which Perry says has the potential of making the party not only the top peacekeeper, but the top spender on the military.

He says increasing the force under the terms laid out by the NDP could involve adding an extra $1 billion per year to the existing $20.1 billion annual defence allocation -- something that might not sit well with the party's base, which traditionally opposes higher spending on the military.

If they weren't prepared to increase spending, it would have to cut elsewhere in the military, Perry said.

"Expanding the army to sustain that kind of force would require either a major rebalance of how money is spent right now -- or a budget increase," he said.

The NDP has been careful to say that its defence commitments hinge on a year-long priority-setting policy review.

Canada is currently ranked 62 out of 126 nations in terms of troop contributions to UN missions. There are 88 personnel -- 54 police and 34 soldiers -- assigned to peacekeeping. The NDP promise is specific to the military.

Depending on the definition of "western," Italy could be ranked No. 1 with 1,100 soldiers -- or South Africa with 2,100. Bangladesh is ranked top overall at 7,800.

Perry says recruiting for regular force regiments would have to be increased to meet the commitment. Currently, many of them operate at reduced levels and for deployments -- such as the Afghan war -- the ranks had to be augmented with thousands of reservists.

Perry says both the navy and air force have their own personnel shortages and it would be hard for a NDP government to avoid an overall increase in the size of the force -- something Conservatives promised a decade ago but quietly abandoned as too costly.

Both the NDP and the Liberals have stressed the desire to return the Canadian military to a peacekeeping role, even though there are fewer traditional ceasefire observer missions in the world.

The UN recently put out a call for nations to contribute 30,000 more troops to trouble spots around the world, a plea answered in large part by China, which pledged 8,000 soldiers and $1 billion in new funding.

Beijing says its goal is to make China the No. 1 contributor in the world.

The decline of Canada's involvement in UN missions can be traced to the searing experiences of the 1990s, where dangerous international missions, such as Rwanda, were hamstrung by bureaucratic indecisiveness. The resulting slaughter of civilians -- both there and in Bosnia -- saw the federal government gravitate towards peace enforcement campaigns, sanctioned by the UN, but under the umbrella of NATO.

One of those missions was Afghanistan, which the NDP opposed after it erupted in open combat in 2006.