OTTAWA - Prime Minister Stephen Harper heads north Monday for his annual Arctic pilgrimage, a trip that comes as Canada and Denmark begin exploring closer military co-operation in the barren region.

He'll visit Iqaluit, Yellowknife, Whitehorse and other communities, but the highlight is the boarding of the frigate HMCS Toronto and the submarine HMCS Corner Brook during an anti-submarine warfare exercise.

It's a demonstration of Canada's sovereignty in the warming archipelago where Russian and American subs have long prowled.

Canada and Denmark have quarrelled over control of Hans Island, but they quietly began forging closer military links recently - an evolving process that underlines a growing dependency as each tries to stake their claim in the potentially mineral-rich North.

A Royal Danish Air Force Challenger jet visited several gravel airstrips at remote Canadian high Arctic outposts last month. They went largely under the public radar, but were - according to a Danish press release - part of "preparations for further co-operation with Canada."

Rob Huebert of the University Calgary said military commanders from both countries have apparently met to talk about areas of common concern and co-operation, in particular northern search-and-rescue missions.

"I know the two sides are talking to each other on a greater level than has been the past," Huebert said.

"It's the idea that if you are going to have search and rescue, if you are going to have an environmental disaster, if you are going to have smugglers, the reality is the infrastructure - the capabilities of any one country is so thin, you're probably not going to be able to deal with it by yourself."

"Even if they do everything (the Conservatives) have promised to do, we're still going to be pretty thin on the ground and you're going to have to co-operate with your neighbours."

He said the head of Canada's northern command, Brig.-Gen. Dave Miller, has apparently discussed some the nuts and bolts concerns with his counterpart in Greenland, which is a self governing region of Denmark.

That was apparently a follow-on to Chief of Defence Staff Gen. Walter Natynczyk's meeting with his Danish counterpart last winter during a conference on Arctic matters in Iceland.

The recent friendly visits included touch downs in Resolute Bay and at Canadian Forces Station Eureka, where the Danish Challenger plane was considered a novelty because jets usually don't land on the tiny runway, said an online posting by Grnlands Kommando, the local military command.

When the Liberals were in power in 2005, the Danes caused a political flap by landing a military expedition on Hans Island, an uninhabited, desolate 1.3-square-kilometre piece of rock in the strait that separates Ellesmere Island from northern Greenland.

The controversy drew attention to Canada's fuzzy northern border and galvanized the Conservatives to make the Arctic one of their political crown jewels.

Harper promised, among other things, a beefed up military presence in the region, starting with three armed, heavy icebreakers, a winter warfare school and a year-round naval base.

But the enormous cost made him think twice.

Plans were eventually modified in favour of six light icebreakers, which, because of cost, have had their capabilities watered down. Plans for a deep-water port and warfare centre are still in the conception stage.

Last year, Harper announced Ottawa's intention to build a heavy icebreaker for the coast guard to replace the aging Louis St. Laurent and the government recently laid out its Northern Strategy in document form.

Huebert said the challenge for the Conservatives now is to move beyond the rhetoric.

"They keep promising and repackaging things," said Huebert, one of the country's foremost academics in Arctic study.

"I'm seeing a lot of smoke and mirrors and not a lot of action."