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.

The U.S. Congressional Budget Office, however, puts the lowest end cost for such a space-based shield at $161 billion (US). The price tag for a higher end system would be between $542 billion and $831 billion, depending if costs can be reduced for launching sensor satellites, the office noted.