WASHINGTON -- As the nuclear Non-Proliferation Treaty comes up for renewal next month, the United States' determination to block the spread of nuclear weapons faces its most severe challenge since the pact was signed a generation ago.
The sale of nuclear fuel or technology by cash-strapped republics of the former Soviet Union to hostile Third World FTC nations or terrorists is a constant fear. North Korea repeatedly threatens to break its agreement with the United States and resume acquiring a nuclear arsenal.
In addition, Iran has what U.S. officials call a crash program to develop nuclear weapons. And the world is struggling to keep track of tons of plutonium, which could be turned into nuclear weapons by rogue regimes.
These threats raise the stakes for the treaty conference that is scheduled to open in New York next month, a meeting shaping up as an important test of U.S. diplomatic leadership and of the world's ability to curb weapons of mass destruction.
The treaty, which went into force in 1970, bars the five acknowledged nuclear powers -- the United States, Russia, China, Britain and France -- from transferring nuclear weapons technology to other nations and forbids states that don't have nuclear weapons to acquire them.
A total of 172 nations have signed the treaty -- on the understanding that they would decide in 1995 whether to keep the agreement in force indefinitely or for only a limited length of time.
After lobbying leaders around the world, the United States and its allies express confidence that they will get the majority votes necessary for the treaty's indefinite extension, fulfilling one of President Clinton's key foreign policy goals.
"We're going to make it happen," Lynn E. Davis, undersecretary of state for international security affairs, said in an interview.
Anything short of indefinite extension, U.S. officials fear, would tempt nations to keep alive the option of developing nuclear weapons. But a number of countries have pushed for renewing the treaty for only a fixed period or for a rolling series of 25-year extensions.
Signed at the height of the Cold War, the NPT calmed fears in the United States and elsewhere that dozens of countries might quickly develop nuclear weapons. It also helped pave the way for later U.S.-Soviet arms agreements.
"It is one of the most important and successful arms-control treaties in history," says Dunbar Lockwood of the independent Arms Control Association. "It establishes a global norm that the spread of nuclear weapons is not in the international community's interest."
In recent years, both South Africa and Argentina renounced their nuclear programs and joined the treaty as nonnuclear states. So have the former Soviet republics of Ukraine, Belarus and Kazakhstan.
But the treaty didn't end proliferation. It failed to enlist all potential nuclear powers or even to control its own members completely.
Israel, which by the late 1960s had begun to assemble a nuclear arsenal, is thought to have up to 200 warheads. It refuses to sign the treaty. Two other holdouts are India, said to have components and fuel for about 20 nuclear bombs, and India's chief rival, Pakistan, said to have material for about 10 nuclear bombs.
Some experts argue that it was the Cold War that prevented even more countries from developing nuclear weapons, since the United States and Soviet Union were able to exert a combination of protection and restraint on their respective allies.
With the Cold War over, the West and its allies are finding it harder to keep other nations out of the nuclear club -- or to persuade them to support the treaty's indefinite extension.
The Clinton administration's drive to win support for the treaty has been complicated by U.S. ties with Israel.
Egypt has refused to agree to indefinite extension of the Non-Proliferation Treaty unless Israel signs. Neither U.S. pressure nor veiled hints of a cut in Egypt's annual $2 billion in U.S. aid have broken the impasse. And because of its size,
history and importance, Egypt could sway much of the Arab world.
The period leading up to the renewal conference has also highlighted the split between advanced nations protected by the nuclear umbrella and developing nations that aren't.
The treaty includes an implicit contract between the two groups: In return for not acquiring the bomb, developing nations were to gain access to peaceful nuclear technology. They also won a pledge that the nuclear states would pursue nuclear disarmament.
Many of the developing states say the nuclear powers have failed to live up to their side of the bargain. Those developing nations want to maintain pressure on the nuclear states by limiting the treaty's terms to a fixed period or by setting a "rolling" series of renewal dates.
Those resentments have left some important regional powers sitting on the fence.
Despite two years of lobbying, South Africa remains noncommittal, even after a recent letter to President Nelson Mandela from Colin L. Powell, the former chairman of the Joint Chiefs of Staff. Most of Africa is also uncommitted.
Indonesia, a major power in the Pacific, opposes indefinite extension.
Latin America is divided, with Argentina lined up with the United States, Venezuela supporting only a limited extension and Mexico undecided.
To capture votes from these key players, U.S. officials have been touting recent moves toward global disarmament, including negotiations for a comprehensive nuclear test ban, a U.S. proposal to halt the production of nuclear weapons fuel, and new talks on sealing off the fuel from dismantled Soviet nuclear weapons.
But the nuclear powers themselves are divided. The United States and Russia are embroiled in a bitter dispute over how to implement the treaty, with Russia refusing to halt its $1 billion-plus deal to help Iran develop civilian nuclear power.
While that deal is technically legal under the treaty, the United States fears that the presence of Russian nuclear experts will allow Iran to acquire dangerous knowledge.
In another major-power split, China is at odds with the four others over what security assurances to give the nonnuclear states.
Some outside experts fear that in the current testy climate, support for renewing the treaty could weaken as next month's conference proceeds, instead of building to the overwhelming majority that U.S. officials seek.
A bare majority in support of the treaty would not boost worldwide confidence that the terms will be obeyed, these experts say.
"If that's the nature of the majority, it will be resented and sneered at by large countries," says James Leonard, a former U.S. arms control negotiator who is now with the Washington Council on Non-Proliferation.