The USSR collapsed in late 1991. Eleven of the twelve members of the Commonwealth of Independent States signed a declaration on December 21, 1991, agreeing that "Member states of the Commonwealth support Russia in taking over the USSR membership in the UN, including permanent membership in the Security Council." One day before the resignation of Soviet President Mikhail Gorbachev, Ambassador Y. Vorontsov transmitted to the UN Secretary-General Javier Pérez de Cuéllar a letter from President of the Russian Federation Boris Yeltsin stating that: