(Reuters) - U.S. President Barack Obama will host top officials from 46 nations at a summit this week aimed at preventing nuclear terrorism.
The main goal of the Nuclear Security Summit in Washington on Monday and Tuesday is to find ways to prevent the spread of nuclear materials and know-how.
Here are some details of official and unofficial nuclear powers and their weapon stocks:
* UNITED STATES: Under a new treaty, a successor to the 1991 Strategic Arms Reduction Treaty (START), the United States and Russia will limit the number of operationally deployed nuclear warheads to 1,550 — 30 percent lower than the ceiling the 2002 Treaty of Moscow established for each side by 2012.
The new treaty, which is to be signed on Thursday, will not come into force without its ratification by lawmakers in both countries.
According to the START counting rules, as of January 2009 the United States had an estimated 5,200 nuclear warheads and 2,700 operationally deployed warheads (2,200 strategic and 500 nonstrategic).
The 2002 Treaty of Moscow (the Strategic Offensive Reductions Treaty, or SORT) between the United States and Russia, states that each country must reduce their deployed strategic nuclear forces to 1,700-2,200 warheads by 2012.
Obama’s “Prague Speech” in April 2009 committed the United States to the long-term goal of zero nuclear weapons.
* RUSSIA: Russia is estimated to have around 14,000 nuclear weapons, although the total is uncertain because there is no accurate count of tactical weapons. Under provisions of START I, the Russian nuclear arsenal has been reduced to around 3,909 strategic nuclear warheads as of January 2009.
* FRANCE: France has been a party to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) since 1992. In 2008, President Nicolas Sarkozy announced the country would leave its submarine missile arsenal in place while cutting its stock of air-launched weapons by a third to around 290 warheads.
As of September 2008, France had already pared its arsenal to about 300 nuclear warheads.
* BRITAIN: Its nuclear stockpile consists of fewer than 200 strategic and “sub-strategic” warheads on four Vanguard-class nuclear-powered ballistic missile submarines. As the first two submarines of the fleet will be retired in 2024, in early 2007 British lawmakers accepted a plan to design a new class of replacement nuclear-armed submarines.
However, with a new Strategic Defense Review due to be conducted after next month’s general election, the merits of renewing Britain’s Strategic Trident system will again be an issue of contention.
* CHINA: China is estimated to have about 250 strategic and tactical nuclear weapons and sufficient stocks of fissile material to produce a much larger arsenal. It acceded to the NPT in 1992 as a nuclear weapon state. China has pledged not to use nuclear weapons against non-nuclear weapons states.
* NORTH KOREA: North Korea promised to abandon its nuclear programs in 2005 but later backed away from the agreement, testing nuclear devices in October 2006 and in May 2009.
It has refused to resume “six-party” talks with South Korea, China, Japan, Russia and the United States on curbing its nuclear ambitions.
Experts believe North Korea, which announced its withdrawal from the NPT in January 2003, has produced enough plutonium for six to eight bombs.
* INDIA: India has formally declared itself a nuclear weapon state. New Delhi is likely to have manufactured weapons-grade plutonium for at least 100 warheads. A 2007 report from the International Panel on Fissile Materials estimated 50-60 warheads had been assembled.
* PAKISTAN: Pakistan is believed to have stockpiled about 580-800 kg (1,279-1,764 lb) of highly enriched uranium, sufficient to build 30 to 50 fission bombs. According to the United States, China helped Pakistan by providing nuclear-related materials, scientific expertise and technical assistance.
Pakistan’s poor record of preventing attacks on even secure military targets has raised concern that militants could penetrate a nuclear facility. Analysts say that while there is minimal risk insurgents could get their hands on a nuclear missile, there is a danger they could steal some fissile material which could be used to build a “dirty bomb.”
Neither India nor Pakistan are signatories to the NPT.
* ISRAEL: Israel is widely believed to possess a sizable nuclear arsenal but maintains a policy of nuclear ambiguity. Based on estimates of the plutonium production capacity of the Dimona reactor, Israel has about 100-200 advanced nuclear explosive devices. Officially, Israel has declared that it will not be the first to introduce nuclear weapons into the Middle East. Israel has not signed the NPT treaty.
* IRAN: Iran has been a non-nuclear-weapon state party to the NPT since 1970. It has a uranium enrichment program which it says is to produce energy. Western powers suspect Iran is trying to develop the means to make atomic bombs because of its past failure to declare nuclear facilities to the U.N. nuclear watchdog and continued restrictions on U.N. inspections.
Iran is under U.N. Security Council sanctions for refusing to suspend uranium enrichment and the United States is leading a push at the United Nations to impose additional punitive measures on Tehran.
U.S. officials cite estimates that Iran, which denies it is seeking to build nuclear weapons, could have a nuclear weapon by the middle of this decade.
Sources: Reuters, www.nti.org (Nuclear Threat Initiative), Congressional Research Service
Reporting by David Cutler, London Editorial Reference Unit, Editing by Philip Barbara and Eric Walsh