The ninth member of the Nuclear Club?

North Korea 's claim of a successful nuclear weapon test, if true, formally makes it the ninth nation known or generally thought to possess such arms.

A glance at the world's nuclear weapons states and their stockpiles, based on estimates compiled from different sources:

North Korea: Believed to have enough fissile material for about a half-dozen weapons, but estimates vary widely and are unverifiable. Claimed first successful nuclear test explosion today.

United States: More than 5,000 strategic warheads, more than 1,000 operational tactical weapons - meant for the battlefield and less powerful than the strategic arms - and approximately 3,000 reserve strategic and tactical warheads. Became the first country to carry out a nuclear test explosion on July 16, 1945.

Russia: Nearly 5,000 strategic warheads, and approximately 3,500 operational tactical warheads. In addition, it has more than 11,000 strategic and tactical warheads in storage. Exploded its first bomb in 1949.

France: Approximately 350 strategic warheads. Exploded its first bomb in 1960.

China: As many as 250 strategic warheads and 150 tactical warheads. Exploded its first bomb in 1964.

Britain: About 200 strategic warheads. Exploded its first bomb in 1952.

India: Between 45 and 95 nuclear warheads. Exploded its first bomb in 1974.

Pakistan: Between 30 and 50 nuclear warheads. Exploded its first bomb in 1998.

Israel: Refuses to confirm it is a nuclear weapons state but is generally assumed to have up to 200 nuclear warheads. Unknown when Israel might have carried out a test explosion.

Sources: Arms Control Association; Nuclear Threat Initiative.