Such recognition was part of the 1992 Yalta Agreement, which divided the Black Sea fleet, and of the 1997 leasing contract that allowed the fleet to remain in Sevastopol. Ukraine’s territorial integrity was also recognized in the 1994 denuclearization agreement, signed by the United Kingdom, Russia, and the United States, and again in April 2011, when then-President Viktor Yanukovych extended the Sevastopol lease.