While the Canadian military is preparing to work with the U.S. on upgrading North America's aging defences, Canada's top general says there have been no talks about joining its ballistic-missile shield program.

Chief of the Defence Staff Gen. Jonathan Vance's comments come amid swirling questions over Canada's potential involvement in ballistic-missile defence, particularly given rampant concerns about North Korea.

Defence Minister Harjit Sajjan appeared to leave the door open to participating in the controversial program in October, but the government has otherwise remained largely ambiguous when asked about missile defence.

The opposition parties, meanwhile, are sharply divided, with the Conservatives saying Canada should start immediate talks with the U.S. while the NDP has strongly opposed any Canadian participation.

Vance told The Canadian Press that Canadian military officials are preparing for what are expected to be in-depth talks with the U.S. about upgrading the North American Aerospace Defence Command, or Norad.

Those discussions are expected to focus on what new and emerging threats the joint U.S.-Canadian system — currently used to spot potential enemy airplanes, missiles and ships — should be able to guard against.

"What I am happy about is we're going to take a holistic view of the military defence of the continent over the next 20 to 50 years," Vance said in an interview Thursday.

"What is occurring out there that could come here in a military way that could impact the safety and security of Canadians, and in the Norad context, of Americans as well?"

Other threats

Ballistic missiles will be one threat that is considered, he acknowledged, especially as countries like North Korea attempt to acquire and expand their missile and nuclear capabilities — but there will be many others like cyber threats.

"Continental defence is not a simple binary 'yes' or 'no' about BMD, and it would be improper to boil it down to just that," Vance said. "Continental defence is about a lot of things."

Vance could not say when those discussions would actually start.

But when asked specifically whether there had been any talks between Canadian military officials and their American counterparts about joining the current U.S. ballistic-missile defence system, Vance was categorical.

"None whatsoever. Absolutely not," he said, before noting that the Liberal government's recent defence policy explicitly said that Canada's position of non-participation remained in effect.

"Therefore, it would be highly inappropriate at this juncture for us to engage in a discussion about BMD."

U.S. won't protect Canada

Many Canadians were stunned in September when the deputy commander of Norad, Lt.-Gen. Pierre St-Amand, revealed that the current U.S. policy is not to intervene in the event of a ballistic-missile attack on Canada.

The revelation came amid growing concern about North Korea's nuclear and ballistic-missile capabilities, which the country has showcased numerous times with a variety of tests in recent months.

U.S. Defence Secretary James Mattis has said the latest test earlier this week showed North Korea is continuing to build missiles that can "threaten everywhere in the world." But Vance said the rogue state still doesn't have the ability to reach Canada with a missile, and that "we're protected against the threats that exist now."

The U.S. actually invited Canada to join its continental missile-shield system more than a decade ago, but then-prime minister Paul Martin opted against it in 2005 following a divisive national debate.

Canada has been on the sidelines ever since as the U.S. spent more than $100 billion building a series of land- and sea-based interceptors to stop the type of limited attack North Korea might launch.