U.S. President Joe Biden formally welcomed Finland and Sweden into the NATO alliance as he signed the instruments of ratification on Tuesday. The U.S. became the 23rd ally to approve their NATO memberships, with Biden also urging the remaining members to complete their own ratification process "as quickly as possible." The North Atlantic Treaty Organization's rules require the consent of all of its 30 existing members before Finland and Sweden can officially join, which is expected in the coming months.