Nations that choose to develop nuclear weapons do so for a variety of reasons, but mostly for national security.

Adding nuclear weapons to a nation's conventional arsenal is a matter of choice. Nations like Pakistan and North Korea have opted to pursue nuclear arsenals. Others, like South Africa, Ukraine and Kazakhstan got rid of their stockpiles after deciding that nuclear arms did not serve their best interests.

Quest for Power

Nicholas Roth, Advocacy and Research Director at the Washington-based Nuclear Age Peace Foundation, says several factors shape a nation's decision to develop nuclear weapons.

"Nuclear weapons are the equivalent of power, the way things are set up right now. If you look at the U.N. Security Council, the five permanent members are all nuclear power states. If you look at the dominant economic powers in the world right now, those are nuclear weapons states too," says Ruth. "Countries like North Korea see that and are motivated to develop nuclear weapons programs based on that. In addition, if you look at the countries where proliferation has occurred- - India, Pakistan and North Korea- - those are volatile areas. So there are security issues that come into it as well."

Most experts agree that security and fear of perceived threats are the main reasons why nations develop nuclear weapons.

Leonard Spector, Deputy Director of the Monterey Institute of International Studies' Center for Nonproliferation Studies, says countries that feel threatened by larger states use nuclear arsenals to strengthen their military defense, as in India's case, and bolster their international standing.

"Originally, the Indian program was very limited until China conducted a nuclear test in 1964. And that led the Indians to reexamine their situation. So in the Indian case, it's certainly a mix of genuine outside threats- - I think they consider Pakistan to be a threat of some kind now that Pakistan has nuclear capability - - and there's also a dimension of prestige," says Spector. "India considers itself a great nation. And these weapons, unfortunately, are often considered to be hallmarks of greatness in the international community." But prestige, according to Spector, is more a by-product of having nuclear arms than a reason to develop them.

Economic Factors

Another factor that affects a nation's choice to pursue nuclear arms is cost. Physicist David Albright, President of the Institute for Science and International Security, notes that some countries choose to build nuclear arsenals because they are cheaper to develop and support than large, standing militaries.  Albright adds, "It can cost hundreds-of-millions of dollars to build a nuclear weapon- - probably close to a billion dollars if you want to build lots of them- - particularly if you want to be able to deliver those nuclear weapons by missiles. But it would be tens-of-billions of dollars or even hundreds-of-billions of dollars to build a conventional military force."

While many experts agree that nuclear weapons are less expensive to maintain than conventional forces, some, like Michael Levi, at the Council on Foreign Relations in New York, say it is not cost that shapes a nation's decision to develop atomic bombs.

"You don't simply acquire nuclear weapons because you can afford to. You acquire them because you think they'll increase your security. And most states have decided that acquiring nuclear weapons will not increase their security. And different states pursue different military capabilities depending on what they believe they need for their security," says Levi.

Pakistan, for example, considered a nuclear arsenal vital for its security as a deterrent against an attack, particularly by neighboring nuclear-armed India.

Help from Pakistan

At the same time, the Pakistani program enabled other countries to develop nuclear arsenals, says Leonard Spector of the Monterey Institute of International Studies.  "The A.Q. Khan [the scientist who developed Pakistan's nuclear bomb] network, the Pakistani nuclear scientist, sold very advanced technology that Pakistan had mastered to North Korea and Libya and Iran. So that gave these three countries an enormous boost in terms of capabilities," says Spector. "But Libya has renounced this and given up all its technology. North Korea does not seem to be exploiting this particular way to nuclear weapons very successfully. And Iran, I think, is the one that is pursuing it [i.e., a nuclear weapons program] more and more actively."

Iran, which the international community believes may be enriching uranium to develop an atomic bomb, says its nuclear program is meant for peaceful purposes.

But David Albright of the Institute for Science and International Security says the type of civilian facilities Iran is using can easily be converted for military use. "The gas centrifuge plant that enriches uranium for civil purposes can be rapidly converted to make highly enriched uranium for nuclear weapons. So a gas centrifuge plant is inherently a nuclear weapons-capable facility. And the Indians used a civil program to gain the capability, which they then converted to nuclear weapons purposes. But the initial effort by India was a civil one," says Albright.

With this record in mind and with North Korea's recent test of a nuclear device, some experts fear more countries may decide to build atomic bombs. Others say it is too early to tell.

But some observers argue that nuclear armament is reversible. They point out that nations like Brazil and Argentina chose not to pursue nuclear weapons even though they had the technology to do so. And they cite the example of South Africa, Kazakhstan and Belarus - - all of whom gave up atomic arsenals because they did not serve their interests. And some experts note that more than 60 years after the dawn of the atomic age, only nine countries have produced nuclear weapons.

That, many analysts say, rekindles the hope that more nations will choose not to develop nuclear weapons because they see themselves better off without them.

This story was first broadcast on the English news program,VOA News Now. For other Focus reports click here.