Some experts are worried about the cost and timeline of U.S. President Donald Trump's proposed "Golden Dome" missile defence system, which Canada has expressed interest in joining. They also say it could set off a space-based arms race that would escalate global tensions.

PM Mark Carney's office says there are "active discussions" on the Golden Dome, but it's too early to say how Canada would join or pay in.

Canadian Prime Minister Mark Carney says his government is talking to the U.S. about joining President Donald Trump’s future Golden Dome missile defense program.