WASHINGTON (AP) — The Biden administration is proposing to Russia a five-year extension of the New START treaty limiting the number of U.S. and Russian strategic nuclear weapons, a U.S. official said Thursday.

The proposal was being communicated to Russian officials, said the official, who spoke on condition of anonymity to discuss a matter not yet publicly announced by the administration.

The treaty is set to expire in February and is the last remaining agreement constraining U.S. and Russian nuclear weapons.