LONDON - Britain offered its first public accounting of its nuclear arsenal Wednesday, disclosing that it has a stockpile of 225 warheads in a move that offers transparency to nonnuclear states in hope of winning stricter global controls on the spread of atomic weapons.

The announcement, made without fanfare in the House of Commons, follows the Obama administration's disclosure that the United States has stockpiled 5,113 nuclear warheads and "several thousand" more retired warheads awaiting the junk pile - the first public description of the secretive arsenal born in the Cold War and now shrinking rapidly.

The United States made the announcement at the May 3 opening of a five-year review of the Nuclear Nonproliferation Treaty, considered the cornerstone of global disarmament efforts, where Washington and its allies are seeking stronger measures to prevent the spread of nuclear arms. Britain made its announcement as the monthlong conference at the United Nations nears an end Friday, with intense debate under way on a final document.

"We believe that the time is now right to be more open about the weapons we hold," Foreign Secretary William Hague told the House of Commons. "We judge that this will assist in building a climate of trust between nuclear and nonnuclear weapons states and contribute, therefore, to future efforts to reduce the number of nuclear weapons worldwide."

Britain had earlier disclosed that it possessed 160 operational warheads, but Hague's comments that the country's "overall stockpile of nuclear warheads will not exceed 225 warheads" was the first time the maximum size of the total stockpile was revealed. The Foreign Office later said the 225 figure was the number of warheads the country holds.

Countries that do not possess nuclear weapons have long demanded more openness from the nuclear-weapon states - the United States, Britain, France, Russia, and China - about the size and nature of their arsenals as an essential step toward nuclear disarmament, which is a key plank in the Nuclear Nonproliferation Treaty. Four other nations have or are suspected of having atomic arms - Israel, India, Pakistan, and North Korea.