Under the START, the United States and Russia are to slash their strategic nuclear warheads to 1,550 each over seven years, about a third less than currently permitted, and the number of delivery vehicles -- missiles, bombers -- will be brought down to 700-800.
The Pentagon earlier this month unveiled the size of U.S. nuclear arsenal for the first time, saying it has a total of 5,113 nuclear warheads in its stockpile.
The White House said the new structure is based on the policies and principles in the Nuclear Posture Review and describes a " comprehensive plan for sustaining a strong nuclear deterrent for the duration of the New START Treaty and beyond."