A US judge has issued a preliminary injunction barring the Trump administration from implementing a new policy that would have allowed for the rapid deportation of hundreds or thousands of migrants to countries other than their own.

The policy, which was set to be implemented, would have denied migrants the opportunity to demonstrate a fear of persecution, torture, or death in the country they were being deported to.

US District Judge Brian Murphy in Boston had previously issued an order temporarily blocking the administration's ability to fast-track deportations, particularly for migrants with legal protections preventing their return to their countries of origin.

The preliminary injunction will remain in place until the ongoing litigation is resolved, effectively halting the implementation of the policy.