|Despite the end of the Cold War, the world's stockpile of nuclear weapons remains high [AFP]
The world's current stockpile of nuclear bombs and warheads is enough to destroy humanity several times over, but the exact number of weapons in existence remains unknown.
This is because most countries guard the numbers as closely held national security secrets.
Nonethess, in the decade and a half since the Cold War ended, the world's combined stockpile remains high with non-proliferation analysts estimating there are currently around 23,000 weapons in existence - nearly half of which are operational, or ready to use at any time.
According to data and estimates compiled by the Federation of American Scientists, the following is a breakdown of the countries that possess - or are believed to possess - nuclear weapons.
Russia is believed to have the world's largest nuclear arsenal, with as many as 12,000 warheads. As the former Soviet Union, it was the second country to develop a nuclear weapon, conducting its first test in 1949.
In 1961 it tested the world's most-powerful weapon, a hydrogen bomb dubbed the 'Tsar Bomba', with a blast equivalent of more than 50 megatons of TNT.
The United States possesses the second largest nuclear arsenal, with a total inventory of around 9,400 nuclear bombs and warheads.
It developed the first atomic weapon during World War Two, under the top secret "Manhattan Project", and tested the world's first nuclear weapon in 1945. The US remains the only country to have used nuclear weapons against another nation - Japan.
France has an estimated 300 nuclear arms, having conducted its first nuclear test in 1960.
Most of its weapons are believed to be deployed on submarines or on air-launched missiles.
China is said to possess around 240 warheads, although it remains unclear how many are fully operational and how many are in storage.
The country first tested a nuclear device in 1964 and is believed by the Pentagon to have about 20 nuclear armed intercontinental ballistic missiles capable of hitting the US.
The United Kingdom has around 185 nuclear weapons, and first tested a device in 1952.
All of the UK's nuclear forces are deployed on missiles carried on the Trident submarine fleet. One Trident submarine is kept on constant deployment at any one time.
While, Russia, the US, France, China and the UK are signatories to the Nuclear Non-Proliferation Treaty (NPT), there are three, and possibly four other nuclear-armed nations who are not. They include:
Pakistan is believed to have around 90 warheads and is thought to have begun covert development of nuclear weapons in the late 1970s after rival India conducted its first "peaceful" nuclear explosion.
Zulfiqar Ali Bhutto, the country's then prime minister, had said a decade earlier that if India built nuclear weapons, Pakistan would do the same, "even if we have to eat grass".
India possesses an estimated 80 warheads and staged its first nuclear test in 1974 using what it called a "peaceful nuclear explosive".
It then conducted a series of tests in 1998, triggering the first nuclear tests by neighbouring Pakistan in response.
North Korea was a member of the NPT, but withdrew in 2003 after the US accused it of having a secret uranium enrichment programme.
It is thought to have conducted two nuclear tests in October 2006 and May 2009, but the degree of success of both tests remains in question. Analysts say there is also little evidence to suggest that North Korea so far has the ability to "weaponise" a nuclear device, to use in an attack on another country.
Israel is not a member of the NPT and refuses to officially confirm or deny having a nuclear arsenal, or having developed nuclear weapons.
Although the government says that the Negev Nuclear Research Centre, located near the town of Dimona is a "research reactor", no reports based on what work is carried out there have ever been published.
Analysts however, estimate that the country holds up to 80 nuclear warheads.
Source: Al Jazeera and agencies