WASHINGTON -- As President Bush and Soviet President Mikhail S. Gorbachev continue their how-low-can-you-go approach to nuclear disarmament, they are responding to the changing nature of the nuclear threat in the post-Cold War era.
The dramatic drawdown of the superpower arsenals and Mr. Gorbachev's willingness to discuss building a U.S.-Soviet "star wars" missile shield show not only that the fear of a nuclear attack by either nation has diminished but also that the greatest menace may now be more primitive atomic weapons being developed by Third World countries.
The mutual effort to reduce each side's tactical nuclear weapons is tacit recognition that the breakup of the Soviet Union poses another and perhaps equally dangerous threat: the possession of nuclear weapons by renegade republics that might use them without thinking through the cataclysmic consequences.
Mr. Gorbachev's ground-breaking agreement to discuss "star wars" would serve his own interests, as well as setting the foundation for even deeper cuts in long-range nuclear weapons.
"The Soviet Union is sitting right where a lot of countries can hit them right now," said Representative Les Aspin, D-Wis., chairman of the Armed Services Committee.
Members of Congress have been meeting behind closed doors in recent weeks, ironing out a 1992 military budget that Mr. Aspin and other lawmakers believe will permit the United States to begin building a ground-based anti-missile shield.
Making such a shield a joint U.S.-Soviet effort could lead to deep cuts in both sides' nuclear stockpiles, according to Stansfield Turner, the retired admiral who headed the CIA during the Carter administration.
"The only way we can ever build the Strategic Defense Initiative is jointly with the Soviets," he said. If only the United States possessed a shield, Mr. Turner said, the Soviets would be compelled to keep their nuclear stockpile high to overwhelm it.
But if both sides cooperated and developed a mutual system, the reduced demands for offensive nuclear weapons would allow each side to cut to about 1,000 strategic warheads, one-sixth the total envisioned under the START accord, he said.
British Prime Minister John Major said yesterday: "There may be a unique opportunity to see a dramatic de-escalation in nuclear weapons." But he also said that his nation would not scrap its plans to deploy nuclear-armed submarines. Britain has 144 nuclear warheads.
France is the other Western European power with nuclear weapons; its forces consist of 158 atomic weapons. Other nations believed to have them include China, India and Israel; nations well along in their development include Brazil, Iraq, North Korea, Pakistan and South Africa.
"The technology is becoming more available to more people," said military scholar James F. Dunnigan, a Pentagon consultant and author of "How to Make War."
"For years, it's been an open joke in the nuclear research community: How many Pakistani nuclear researchers have you run into today?"
China poses a latent nuclear threat to the Soviet Union, Mr. Dunnigan said. "The Chinese want their eastern provinces back [from Moscow], and the next generation [in Beijing] might not be so polite."
Defense officials said the calculations of Third World powers with fledgling nuclear arsenals would be altered if the United States and the Soviet Union lined up against their proliferation and use. "One side won't be able to play off against the other, like we used to fear," said a Pentagon official. In other words, Iraq could not launch a nuclear strike against Israel confident that the Soviet Union would act as a counterweight to U.S. retaliation.
Mr. Bush's unilateral gambit cutting the U.S. tactical nuclear arsenal a little more than a week ago gave Mr. Gorbachev the opening he needed to do the same -- and to deny the small nuclear weapons to both the Red Army and, more important, the increasingly restive Soviet republics.
Russia and three other republics -- Byelarus, Kazakhstan and the Ukraine -- have nuclear weapons on their soil.