Britain announced for the first time on Wednesday that it had set a limit on its nuclear weapons stockpile, at 225 warheads, and said it would re-examine its policy on use of nuclear weapons.
The announcements, timed to coincide with a major U.N. nuclear non-proliferation conference in New York, reflect a drive by Britain's new Conservative-Liberal Democrat coalition government to be more open about the country's nuclear arsenal.
Previously, Britain had only made public the number of operationally available nuclear warheads for its Trident missile-armed submarine fleet, and had given no figure for the overall stockpile.
"For the first time, the government will make public the maximum number of nuclear warheads that the UK will hold in its stockpile. In the future our overall stockpile will not exceed 225 nuclear warheads," Foreign Secretary William Hague told parliament.
The ceiling on operationally available nuclear warheads would stay at 160, he said. The extra warheads are to allow for "processing, maintenance and logistic management", the government said.
Hague said the new government would review Britain's policy on when it would consider using nuclear weapons as part of a wide-ranging defense and security review launched by the new government, which took office after the May 6 election.
Britain had long said it would only consider using nuclear weapons in "extreme circumstances" of self-defense, including the defense of NATO allies, but had been deliberately ambiguous over the precise circumstances of use, he said.
"We've decided that the time is right to look again at our policy as the U.S. has done in their recent Nuclear Posture Review to ensure that it is fully appropriate to the political and security context in 2010 and beyond," Hague said.
Defense Secretary Liam Fox said in a statement Britain remained committed to its nuclear deterrent.
U.S. President Barack Obama last month unveiled a new policy restricting U.S. use of nuclear weapons, for the first time foreswearing their use against non-nuclear countries, provided they complied with the nuclear Non-Proliferation Treaty (NPT).
Hague said he hoped his announcement would help build trust between nuclear and non-nuclear weapons states.
Britain and other nuclear weapons states are striving to prevent the spread of nuclear weapons to countries such as Iran. Those countries often argue that established nuclear powers are doing nothing to reduce their arsenals as the NPT urges.
Hague's announcement may ease strains within Britain's new coalition government over a decision to spend billions of pounds on updating Britain's nuclear deterrent at a time when the country needs to cut a huge budget deficit.
The center-right Conservatives, the senior coalition partner, are committed to replacing the existing nuclear-armed submarine fleet. The center-left Lib Dems called during the election campaign for Britain to look at cheaper alternatives but have pledged not to vote against replacing Trident.
Britain has the smallest arsenal of the five legally recognized nuclear weapons states.
The United States and Russia agreed recently to limit the number of operationally deployed nuclear warheads to 1,550.
In 2008, France said it would leave its submarine missile arsenal in place while cutting its stock of air-launched weapons by a third to around 290 warheads. China is estimated to have about 250 nuclear weapons.