Under the terms of the NPT, which went into effect in 1970, only five countries were allowed to have nuclear weapons. The nuclear powers at that time -- the United States, the Soviet Union, Britain, France, and China -- agreed not to proliferate weapons technology to other countries and to work toward their own eventual nuclear disarmament.
Some 190 countries ratified the treaty. But 36 years later, the world faces a problem. There are now nine nuclear weapon states -- four of them outside the NPT.
And according to IAEA Director-General el-Baradei and other experts, this list could potentially grow much longer. El-Baradei warned at a conference in Vienna on October 16 that it was now becoming "fashionable" for countries to consider going nuclear:
"Unfortunately, the political environment is not a very secure one," he said. "We have seen lots of temptation for the countries to develop nuclear weapons in the last decade or so. It started with Iraq, we then saw Libya. We are still going through verifying Iran's undeclared [nuclear] program for almost two decades. We have seen the nuclear test in North Korea."
El-Baradei said the fact that countries like the United States, Russia, and China continue to rely on their nuclear weapons as a key part of their national defense reinforces the message that having one's own weapons offers the best protection. Many countries, he said, no longer accept what they see as a double standard:
Many experts worry that North Korea's and Iran's nuclear ambitions could be the catalyst for a new round of regional arms races -- especially given the international community's apparent inability to influence Pyongyang and Tehran.
"The world has been better off when countries know that their neighbors are not pursuing nuclear weapons," says Mark Fitzpatrick, a nuclear proliferation expert at the London-based International Institute for Strategic Studies.
"But when neighbors begin to break those agreements, particularly in the Middle East, where there's a great deal of tension, and in Northeast Asia, where there's tension, you don't know exactly how the ripple effects will manifest themselves in countries wanting to have a hedge and develop capabilities that they could put to weapons uses," Fitzpatrick adds.
So what countries have the potential to develop nuclear weapons?
The good news, say experts, is that most of these states are stable democracies with existing civilian nuclear programs. They could, in theory, start reprocessing plutonium for weapons quite easily -- but for now have chosen to abide by their international commitments. These countries include many European states, Japan, Argentina, and Brazil.
But of greater concern are states in the Middle East. "There is a real concern that as Iran gets closer to the day when it could have a nuclear weapon, other states in the Middle East will have to reconsider their own security policies," Fitzpatrick says.
"And some of them will undoubtedly consider whether a nuclear weapon capability is in their interest," he continues. "Egypt is now looking at nuclear energy for entirely legitimate, viable economic reasons. But there undoubtedly is a security element to their thinking. Turkey is expanding its nuclear-power facilities, again for totally legitimate, proper, respected, and transparent reasons. I'm not suggesting at all that either Turkey or Egypt are seeking nuclear weapons. But there is a security element to their pursuit of these technologies."
There are indications Saudi Arabia has also thought about the nuclear option. "Saudi Arabia is known to have entertained visits by the Pakistani weapons salesman, A.Q. Khan," Fitzpatrick says. "Nothing is known about the nature of the discussions Khan had there. There's no evidence that Saudi Arabia is pursuing nuclear weapons. [But] it might think that it has to look at this if Iran gets the atomic weapon."
So is there anything the international community can do? So far, the evidence with North Korea and Tehran has not been encouraging. But Fitzpatrick says there are some steps that can and should be taken to reinforce the Nonproliferation Treaty and its related mechanisms.
"One step is to restrict the expansion of enrichment technology by giving nations a guaranteed means of obtaining enriched fuel for their nuclear power reactors, so they have no need to pursue enrichment on their own," he says. "There was a forum in Vienna last month that addressed this and there's a great deal of attention being given to how to guarantee fuel supply. Other steps that are being looked at include making it harder for nations to withdraw from the NPT, as North Korea did."
Fitzpatrick says existing nuclear powers could set an example by ratifying the Comprehensive Test Ban Treaty as an indication that they are serious about eventually disarming. Among the "founders" of the nuclear club, China and the United States still have not ratified the document.
Experts agree that stopping the further proliferation of nuclear weapons is a task that is part scientific and part psychological.
But doing nothing is not an option. "Think of it as an egg box, whereby the states are the eggs and peace is maintained by the box, which represents a set of rules and principles in international society holding states in place," says Neal Pal, of the U.S.-based Wisconsin Project On Nuclear Arms Control.
"Now, one of these principles or norms is that countries should refrain from developing nuclear weapons," he adds. "But if certain states undermine these norms, then the box becomes fragile, the fabric of international society starts to tear, and there is nothing there to prevent the eggs from hitting each other. And you could get a very messy outcome."
That's a nuclear omelet no one wants to contemplate.
DECLARED NUCLEAR-WEAPONS COUNTRIES:
country warheads (est.) date of first test
United States 10,500 1945
Russia 18,000 1949
United Kingdom 200 1952
France 350 1960
China 400 1964
India 60-90 1974
Pakistan 28-48 1998
North Korea 0-18 2006
Israel is widely believed to possess nuclear weapons, but it has not declared itself a nuclear-armed country.
South Africa constructed six uranium bombs but voluntarily dismantled them.
Belarus, Kazakhstan, and Ukraine all gave up the nuclear weapons that were on their territory when the Soviet Union collapsed in 1991.