WASHINGTON, Oct 11 Pakistan possesses 50-90 nuclear weapons compared to India's 55-115, says a survey released in Washington on Monday.

The survey by a Washington-based nuclear watchdog, the Institute for Science and International Security, also claims that Pakistan has 1,000-1,250 kilograms of highly enriched uranium or uranium 235 enriched to 20 per cent or more.

India also is believed to possess this material, used for making weapon-grade nuclear fuel, but the survey does not reveal how much. India, however, has 300-470 kilograms of plutonium compared to 20-60kg of Pakistan.

Pakistan mainly relies on uranium for making nuclear fuel while India relies on plutonium. The institute that conducted this survey is the same that published a report in 2003 that Dr A.Q. Khan was selling nuclear technology to Iran, Libya and North Korea. Published a year before Dr Khan's confession, the report caused a sensation in the United States but was rejected by Pakistan as speculative.

The new survey reports that military nuclear stocks in India, Pakistan, and Israel are continuing to grow and urges the international community to slap a ban on the production of fissile material for nuclear weapons to prevent further proliferation.

Pakistan, India and Israel are placed in the category of de facto nuclear powers that are still not recognized by the international community as nuclear states. North Korea is listed as an ambiguous state while South Africa is listed as the only country which dismantled its nuclear programme at the end of the Apartheid regime.

According to the survey, Israel has 510-650 kgs of plutonium and has stockpiled 110-190 nuclear weapons. North Korea has 15-38 kgs of plutonium and 2-9 nuclear weapons. And South Africa, although it dismantled its nuclear programmes in the early 1990s, still has a large stock of unirradiated uranium, about 430-580 kgs.

The survey admits that Israel's plutonium and HEU stocks remain difficult to estimate. Similarly, India may now be producing HEU in significant quantities in a gas centrifuge plant it has been working on for many years but the surveyors David Albright and Kimberly Kramer did not have an estimate for India's HEU stocks.

Pakistan's fissile material stockpile, the surveyors say, has always been difficult to assess, but its stock now appears to be large enough to rival that of India. North Korea has produced separated plutonium in unknown quantities during two periods and may now be enriching uranium, the survey warns.

But the total stockpile of fissile material at these five countries is still very small compared to what more advanced nations possess. Describing these stockpiles as huge, the survey says that at the end of 2003 there were more than 3,700 metric tons of plutonium and highly enriched uranium, enough for hundreds of thousands of nuclear weapons, in about 60 countries. Although some fissile material is disposed of, more material is produced, causing the total to grow each year.

The stocks of plutonium and HEU in the world are roughly equal, as are stocks of civil and military fissile material. However, most plutonium is in civil stocks and most HEU is in military stocks.

The world's acknowledged nuclear weapon states hold considerable stocks of military HEU and plutonium. Most of the plutonium and HEU in military stocks is in nuclear weapons, reserves, dismantled weapons, and naval and production reactor programmes.