Washington ? The United States has 5,113 nuclear warheads in its stockpile and “several thousand” more retired warheads awaiting the junkpile, the Pentagon said Monday in an unprecedented accounting of a secretive arsenal born in the Cold War and now shrinking rapidly.

The Obama administration disclosed the size of its atomic stockpile going back to 1962 as part of a campaign to get other nuclear nations to be more forthcoming, and to improve its bargaining position against the prospect of a nuclear Iran.

The U.S. has previously regarded such details as top secret.

The figure includes both “strategic,” or long-range weapons, and those intended for use at shorter range.

The Pentagon said the stockpile of 5,113 as of September 2009 represents a 75 percent reduction since 1989.