The Justice Department’s antitrust division was briefly instructed to pause cooperation with Canadian authorities this week, as trade tensions continue to escalate between the two countries.

Lynda Marshall, chief of the Antitrust Division’s international section, directed officials in a Wednesday email with the subject line “Pause on Canada” to halt cooperation on cases and engagement on policy issues with Canadian authorities, according to emails reviewed by the Wall Street Journal. She did not provide a reason for the directive, saying she would provide further guidance if the policy changed.