The Pentagon says the U.S. maintains 5,113 nuclear warheads in its stockpile and "several thousand" more retired nukes that await dismantling.

Monday's announcement marked the first time the Pentagon has officially disclosed the number. The U.S. has previously regarded such details as top secret.

A senior defense official, speaking on condition of anonymity, says the size of the stockpile represents a 75 percent reduction since 1989.

The release coincides with Secretary of State Hillary Rodham Clinton's address to a United Nations conference checking up on efforts to contain the spread of nuclear weapons around the world.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

WASHINGTON (AP) — The Obama administration is expected to release a more precise accounting of the U.S. nuclear arsenal Monday, military and other U.S. officials said, shedding new light on a secretive arsenal born in the Cold War and now shrinking rapidly.

The release coincides with Secretary of State Hillary Rodham Clinton's address to a United Nations conference checking up on efforts to contain the spread of nuclear weapons around the world.

The move was the subject of a furious debate within the Obama administration that continued until just hours before Clinton's speech.

Exposure of once-classified totals for U.S. deployed and reserve nuclear weapons is intended to put pressure on nations such as China, which has revealed little about its nuclear stockpile.

One U.S. official said Clinton was expected to call on Russia and China to follow the U.S. lead and make more information public. The officials spoke on condition of anonymity because they were not authorized to discuss the issue publicly.

"You can't get anywhere toward disarmament unless you're going to be transparent about how many weapons you have," said Sharon Squassoni, a nuclear policy analyst at the Center for Strategic and International Studies.

It was not clear whether the administration would spell out details such as how many nuclear warheads are strategic, or long-range, and how many are tactical, or shorter-range.

A rough count of deployed and reserve warheads has been known for years, so the Pentagon figures won't tell nuclear experts much they don't already know. Estimates of the total U.S. arsenal range from slightly more than 8,000 to above 9,000.

The warheads are spread among deployed weapons, which are those more or less ready to launch, and reserve weapons.

Russia and the United States have previously disclosed the size of their stockpiles of deployed strategic weapons, and France and Britain have released similar information. All have signed the Nuclear Nonproliferation Treaty, which is the subject of the U.N. review that began Monday.

The U.S. revelations are calculated to improve Washington's bargaining power with Iran's allies and friends for the drive to head off what the West charges is a covert Iranian program to build a bomb.

Iranian President Mahmoud Ahamadinejad spoke ahead of Clinton at the conference, denouncing U.S. efforts to pressure his regime to abandon its nuclear program.

The U.N. conference will try to close loopholes in the internationally recognized rules against the spread of weapons technology.

Independent analysts estimate the total world stockpile of nuclear warheads at more than 22,000.

The Federation of American Scientists estimates that nearly 8,000 of those warheads are operational, with about 2,000 U.S. and Russian warheads ready for use on short notice.

The United States and Russia burnished their credentials for insisting that other countries forego atomic weapons by agreeing last month to a new strategic arms reduction treaty.

The New START treaty sets a limit of 1,550 deployed strategic nuclear warheads for each side, down from 2,200 under a 2002 deal. The pact also re-establishes anti-cheating procedures that provide the most comprehensive and substantial arms control agreement since the original 1991 START treaty.