CIA Director George Tenet says the desire in the world for atom bombs is increasing and that the ?domino theory? of the 21st century may well be nuclear.

That desire may be true of the United States as well. Though it has one of the world's largest nuclear arsenals, the Bush administration is starting research on a new class of smaller nuclear weapons to deal with what it calls emerging threats. Writing in The Washington Post, Secretary of Energy Spencer Abraham described the challenges posed by rogue nations or terrorists possessing weapons of mass destruction: "Henceforth, threats will likely evolve more quickly and less predictably. It is a situation that demands the restoration of our capacity to meet new challenges."

In other words, the United States may need new nuclear weapons.

Is the world in a new nuclear arms race? Recent developments point in that direction. North Korea says it has nuclear weapons, and Iran appears determined to establish a nuclear program. Even U.S.-friendly countries like Brazil are suggesting that they, too, may need nuclear weapons to defend themselves.

Some analysts look back with nostalgia on the Cold War period when there were only two nuclear superpowers which practiced mutual deterrence.

Leonard Spector, Deputy Director of the Center for Nonproliferation Studies in Washington says ?the most significant change is that the countries that are acquiring nuclear arms are adversaries, and this does transform proliferation from what might be considered a diplomatic and global security issue into a direct American national security issue.?

In its search for new ways to stop the spread of nuclear weapons, the Bush administration has launched a preemptive war against Iraq and organized searches of North Korean ships it suspects of exporting missiles or weapons of mass destruction. At home, the administration is planning to revamp the U.S. nuclear arsenal by restarting the production of the plutonium cores of nuclear weapons. It has also succeeded in shortening the preparation time for nuclear tests and in gaining the approval of the U.S. Congress to design low-yield nuclear weapons that may be able to destroy biological, chemical and nuclear weapons in underground bunkers.

Some analysts think these forceful steps, particularly U.S. plans for smaller atom bombs, may backfire. Instead of making the world safer, they could spark a new arms race. Daryl Kimball, Executive Director of the Arms Control Association, says ?these are the most massively destructive weapons on earth. So it's important that we don't cross this line because it could tempt other states to develop similar types of weapons and vastly complicate and increase the dangers of future wars. We have to remember that our actions that we are taking now in the next few years are going to have ramifications that last for decades.?

Critics of the Bush administration's more robust nuclear policy say it could undermine the Nuclear Nonproliferation Treaty, or NPT, which they contend has been at the center of international efforts to stop the spread of weapons of mass destruction. The NPT is based on a pledge by nuclear nations to eliminate gradually their arsenals in return for other countries forgoing such weapons. The non-nuclear states also gain the benefit of peaceful uses of nuclear energy, such as power generation and nuclear medicine.

Sidney Drell, Senior Fellow at the Hoover Institution and former member of a nuclear weapons government advisory committee says ?the question has come up that the United States is talking about the need to develop a new generation of nuclear weapons that are called robust nuclear earth penetrators. The fact that the most powerful country in the world with the strongest conventional forces feels the need to develop new nuclear weapons and probably have to test them -- how does that square with telling other countries that are much weaker than we are that they don't need nuclear weapons

In their defense, Bush administration officials say studies on smaller nuclear weapons are needed to protect the United States. The Pentagon estimates that more than 70 countries have underground facilities, many of which are suspected of sheltering weapons or command centers. The administration cautions it is only researching, not building, new nuclear weapons, and there are no plans to break a decade-long moratorium on nuclear testing.

On other fronts, some analysts support the administration's commitment to diplomacy backed by tougher policies. They say the war in Iraq was waged to enforce United Nations resolutions. And the new policy to search North Korean ships is backing up a five-nation effort to convince North Korea to give up its nuclear weapons program. In Iran, they point out, the United States is supporting the International Atomic Energy Agency, the monitoring arm of the NPT, in its efforts to get more access to Iran's nuclear facilities.

Leonard Spector of the Center for Nonproliferation Studies says that through its three decades of operation, the NPT has not been strictly enforced. He says the Bush administration is justified in pressuring countries to comply with their treaty commitments. ?Historically, the nonproliferation treaty has been an anchor, a really important global statement of what appropriate behavior is, but when you came to dealing with individual countries, many other factors were used. You have these ad hoc tools brought to bear to try to influence these countries. It's a refurbishing of some of the tools we have used in the past and an adaptation of them to the particular circumstances.?

But even supporters of the Bush administration's tougher nonproliferation policy question moves to modernize the U.S. nuclear arsenal. Henry Sokolski, Executive Director of the Nonproliferation Policy Education Center, says ?there is some residual value in being able militarily to knock a country out, and that can be done mostly entirely without nuclear weapons. The idea that we would build up our arsenal in a significant way as a hedge to deter others from getting these things strikes me as totally at odds with the insightful perception that we need to act in advance of countries getting these weapons. I am not arguing that we should get rid of nuclear weapons. I do think we should rely less on these things for security.?

Sidney Drell of the Hoover Institution says the best way to halt programs before they start producing weapons is to support international treaties such as the NPT and strengthen multilateral organizations like the International Atomic Energy Agency with additional monitoring responsibilities and more funding.

Analysts agree the debate over a more active U.S. role in stopping the spread of weapons of mass destruction is just beginning. Will the United States lead by example, working with other countries and adhering to present treaties? Or will it push forward with unilateral plans to develop new nuclear weapons. It may not be able to do both for long.