WASHINGTON -- The U.S. military is preparing to ask that new sensors be installed in the Canadian Arctic that would be able to track different types of incoming missiles.

A senior defence official said Tuesday the request is being made to U.S. policy leaders -- as well as the Canadian government. He said it's too early in the process to set a target date.

"I don't think we have a timetable just yet," said Admiral William Gortney, the head of the Canada-U.S. Norad program and of Northern Command -- the Colorado-based body with tracking responsibility for the U.S. missile-defence program.

"We're just now bringing it up through our policy leaders as well as with the Canadian government."

He told a news conference at the Pentagon that it's nearly time to replace the aging sensors in the Canada-U.S. North Warning System, along the old Arctic distant early warning line, the Cold-War era DEW Line.

He said he'd prefer to replace them with newer versions that could not only see farther, over the horizon, but also be able to track shorter-range cruise missiles.

"In a few years -- I'd say 10 years is the number -- (the current equipment is) going to reach a point of obsolescence and we're going to have to reinvest for that capability," Gortney said.

"The question is, what sort of technology do we want to use to reconstitute that capability? We don't want to put in the same sorts of sensors because they're not effective against the low-altitude, say, cruise missiles. They can't see over the horizon."

The U.S. military has in the past voiced a hope for more flexible sensors in the Arctic, but Gortney's remarks suggested that a more formal request is in the works.

Canada refused a decade ago to join the American ballistic missile defence, or BMD, although it does play a role in monitoring the airspace through Norad. The Arctic sensors would deliver tracking information to the missile-defence program.

Defence Minister Jason Kenney recently said the government would look at modernizing Norad's capacity to detect potential threats.

He also reiterated that it was examining the long-standing opposition to participation in ballistic missile defence and would await the findings of a study by the House of Commons defence committee.

"But up to now, we haven't seen information that has changed our opinion on BMD," Kenney told a news conference call last month.