WASHINGTON, June 10 -- The United States has set a ninety-day clock to rewrite the rules on when a machine may decide to kill. President Trump has ordered the Pentagon and the intelligence agencies to move faster on artificial intelligence and to loosen the constraints that have kept it out of the gravest decisions of war. A national security memorandum he signed last week directs the entire defence establishment to become, in the administration's words, an "AI-first" enterprise, and orders a revision of the foundational policy governing autonomous and semi-autonomous weapons.

The memorandum, designated NSPM-11, rescinds a Biden-era framework the White House dismissed as a tangle of "ideological mandates," and revokes guardrails it judge...