May 24, 2002 Posted: 5:03 AM EDT (0903 GMT)

Confronting each other over the disputed territory of Kashmir, India and Pakistan are the world's newest known nuclear powers.

The two countries conducted back-to-back nuclear tests in 1998, but the exact number of warheads held by each side is unknown.

The following explains how tension in the region began, and includes estimates of their nuclear arsenal supplied by Jane's Strategic Weapon Systems in London.

INDIA

In 1966, India declared it could produce nuclear weapons within 18 months.

Eight years later, India tested a device of up to 15 kilotons and called the test a "peaceful nuclear explosion."

In May 1998, India conducted five underground nuclear test in Pokharan, Rajasthan, and declareed itself a nuclear state.

Estimated nuclear warheads: 100 to 150

Of these, up to 20 are nuclear bombs that could be dropped from Jaguar or Mirage 2000 aircraft.

The remaining warheads could be fitted to Agni or Prithvi missiles

Missile types and ranges:

Prithvi SS-250 (250 km/156 miles)

PAKISTAN

In 1972, following its third war with India, Pakistan secretly decides to start nuclear weapons program to match India's developing capability.

Pakistan responds to India's nuclear tests in 1998 by announcing it exploded six underground devices in the Chagai region (close to its border with Iran.)

Estimated 25 to 50 nuclear warheads, including up to 20 bombs deliverable by F-16 fighter jets

Remaining warheads may be fitted to Shaheen or Ghauri missiles

Missile types and ranges: