The NPT, which went into effect in 1970, also received a rude blow with the unearthing two years ago of an international black market network in technology that could be used to make atomic weapons, run by the father of Pakistan's atomic bomb Abdul Qadeer Khan.

Khan's smuggling ring had been secretly supplying these three nations, labeled by Washington as "rogue states."

Mohammed ElBaradei, head of the Vienna-based International Atomic Energy Agency (IAEA) which verifies compliance with the NPT, has been in the forefront of critics calling for fixes to loopholes in the treaty that make coming to grips with countries like Iran and North Korea difficult.

North Korea kicked out IAEA inspectors in December 2002 and withdrew from the NPT the following month, and now claims to have made atom bombs.

The IAEA has for over two years been investigating Iran on US charges that Tehran is secretly developing nuclear weapons but still has come to no conclusion about whether the Islamic Republic's program is peaceful or not.

Libya was once a major worry but it has dismantled its programs to develop weapons of mass destruction. This however came after negotiations with the United States and Britain, and not from an IAEA, and so NPT-related, initiative.

Iran, experts say, is the crucial test case, with the survival of the NPT at stake if the Islamic Republic develops atomic weapons while under IAEA safeguards.

Iran warned Saturday it might resume uranium conversion within days, a step which would likely torpedo talks with the European Union and result in the EU joining the United States in efforts to bring Tehran before the UN Security Council for possible international sanctions.

ElBaradei told AFP in January that the world cannot continue allowing countries to develop the ability to make nuclear fuel that can also be used to make atomic bombs.

"We just cannot continue business as usual that every country can build its own factories for separating plutonium or enriching uranium.

"Then we are really talking about 30, 40 countries sitting on the fence with a nuclear weapons capability that could be converted into a nuclear weapon in a matter of months," he said.

The NPT had seemed to be working in the past as "many more countries have given up nuclear weapons than have begun them," according to a report from the Washington-based Carnegie Endowment for International Peace.

But the report said there are now "rising doubts about the sustainability of the non-proliferation regime."

Such security doubts mean that "nations with ample technology ability to develop nuclear weapons (such as Brazil and Japan) may be reconsidering their political decisions not to do so," the Carnegie report said.

The question is: can the month-long NPT Review Conference, the seventh such review held every five years since 1970, carry out needed reforms?

Experts are skeptical.

"There is not even an agenda for the meeting yet," non-proliferation expert Gary Samore of London's International Institute for Strategic Studies said.

He said the reason for this is that non-nuclear-weapons states are bitter that promises by nuclear-weapons states to disarm, promises enshrined in the NPT and repeated in "13 disarmament steps" adopted at the previous review conference in 2000, have not been carried out.

In addition, there are lingering issues such as anger by Arab states that Israel, believed to have atomic weapons, has not signed the NPT and thus is not subject to inspection by the IAEA.

India and Pakistan are the other two nuclear states which are not NPT members.

Samore noted that both US President George W. Bush and ElBaradei have proposed moratoriums on making nuclear fuel "but there is no consensus on any of these alternatives."

A diplomat who is to attend the talks said the United States lacks non-proliferation credibility since it is considering developing new nuclear weapons to destroy shelters deep underground known as "bunker busters."

The diplomat said all this leaves non-nuclear-weapons states reluctant to agree to even what is the most likely measure for the review conference, to make an Additional Protocol allowing for wider inspections by the IAEA a universal requirement to all 188 NPT signatory states.

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