On June 25, the frontier of arms control suddenly shifted to the Indian port of Kandla, where customs officials, acting on a tip, demanded to see what else was in the hold of a North Korean ship unloading a cargo of sugar.

They hit the jackpot inside the 9,600-ton steamer Ku Wol San: 148 containers listed on the cargo manifest as "water purification machinery" destined for Malta turned out to contain missile parts, machine tools, and blueprints of a Scud missile, all allegedly bound for Pakistan.

The seizure, disclosed this week, is just the latest example of a disturbing trend. Over the past 15 months, efforts to prevent the spread of weapons of mass destruction have suffered a series of deep setbacks, including the detonation of atomic bombs by India and Pakistan; long-range missile advances by North Korea, Pakistan and Iran; the end of the United Nations weapons inspections in Iraq; and the perverse political lesson some nations have drawn from the war in Kosovo, that nuclear weapons are the only protection against NATO intervention.

"All the trend lines are negative," says Michael Krepon, a disarmament expert at the Henry L. Stimson Center, a Washington-based think tank. "All the usual suspects are moving in the wrong direction."

This summer alone, Pakistan and India have smashed the Cold War theory cited by Pakistani leaders to justify their decision to match India's nuclear tests: that two countries with nuclear weapons would refrain from direct conflict with each other. In addition, U.S. officials say that North Korea, which American officials believe possesses a grapefruit-sized lump of material big enough to make one or two nuclear bombs, is preparing to test a long-range missile capable of hitting much of the western United States.

Reflecting a sense of gloom, one senior State Department official, Martin S. Indyk, recently told a foreign policy forum that the question is no longer whether Iran will obtain nuclear weapons, but rather how the United States will deal with Iran afterward.

Indeed, U.S. policymakers are increasingly turning from "nonproliferation," or preventive measures, to what in defense jargon is known as "counterproliferation": how to deal with countries that acquire nuclear weapons despite preventive efforts. The tools include economic sanctions, research on goo-emitting bombs that could smother chemical weapons and burrowing bombs that could reach buried targets, and "theater missile defense," a reincarnation of the Reagan era "Star Wars" program to intercept missiles in flight.

However, these alternatives raise as many foreign policy questions as they answer. Would the United States really launch a preemptive military strike on a suspected weapons facility? Could theater missile defense backfire and set off a new arms race? Should sanctions imposed on India or Pakistan as punishment after their nuclear tests last year be eased, as some U.S. lawmakers and U.N. diplomats suggest?

For 35 years, the world's small club of nuclear powers has largely kept intact its monopoly on weapons of mass destruction, defying President John F. Kennedy's 1963 prediction that 15 to 20 countries would possess nuclear weapons by the early 1970s.

Nations "of concern" to the United States that are seeking weapons of mass destruction include Iran, Iraq, North Korea, Libya, Syria and Sudan, according to a CIA report to Congress on the second half of 1998 that was declassified yesterday. The Associated Press said the CIA reported that Egypt is trying to buy technology for improved missiles and that India and Pakistan continue to try to improve their nuclear weapons programs.

Recent setbacks follow some major successes in arms control during the early 1990s. A nuclear test ban was signed. Brazil and Argentina scrapped their nuclear weapons programs. South Africa announced it had secretly built six nuclear bombs and then dismantled them. After the collapse of the Soviet Union, three newly independent, former Soviet republics gave up their nuclear weapons. That left the five major nuclear powers -- the United States, Britain, France, Russia and China -- as well as Israel, widely suspected of having dozens of nuclear bombs.

Now, however, the tide is turning. Iraq is importing material that could be used for biological weapons and seeking to buy nuclear bomb material, according to former weapons inspectors.

"We have destroyed the production" of nuclear weapons-grade material, says Rolf Ekeus, Sweden's ambassador to the United States and former head of the U.N. inspection effort. But he notes that Iraqi weapons makers "have done all the calibrations and calculations. Our concern is that they are buying [the material] and once they do that, the rest of the work is already done."

American officials believe that within five years Iran will have the ability to make a nuclear bomb, even though the United States persuaded Russia and China to curtail their nuclear cooperation with Tehran. Iran already possesses medium-range missiles and is working on long-range missiles with help from Russian firms and North Korea.

Economically strapped Pakistan recently let the Saudi Arabian defense minister and a delegation from the United Arab Emirates tour its nuclear bomb and missile development sites. Though Shahid Hamid, governor of the Punjab region, said in an interview that Pakistan's nuclear technology "is not for sale," he conceded that "there have been offers made to us by others" seeking to buy nuclear secrets.

NATO's war over Kosovo has also complicated efforts to persuade nations to forgo nuclear weapons. On May 13, European Union representatives met in New York with China's chief arms control negotiator to prepare for a new round of treaties aimed at limiting the spread of nuclear weapons. Because NATO had accidentally destroyed China's embassy in a bombing raid on Belgrade six days earlier, the Europeans were not sure the Chinese would even show up.

But they did -- and delivered a stern lecture. NATO countries were the ones destroying nonproliferation efforts with their war in Kosovo, China's representative, Sha Zukang, said, according to a German diplomat. Sha added that NATO showed it wouldn't respect any country unless that country had nuclear weapons.

On June 3, the European Union met with Russian arms negotiators, who delivered the same message.

In between, William J. Perry, acting as special envoy for President Clinton, took a U.S. delegation to North Korea for the highest-level talks between the two countries since the Korean War. Holding out the possibility of normal relations with the United States, Perry pressed North Korean leaders to scrap efforts to develop long-range missiles and stick to their commitment not to build the bomb. According to participants, the North Korean leaders replied, in essence: Why should North Korea give up those weapons? If it did, the United States might start complaining about human rights in North Korea and bomb it into oblivion like Serbia.

The Clinton administration is pursuing an ad hoc policy toward each proliferation threat around the world. Iraq has been bombed for seven months, the first war waged exclusively over the issue of weapons proliferation. North Korea has been both cajoled and threatened. The United States has waged a campaign to block international and commercial nuclear cooperation with Iran. Israel's nuclear weapons have been ignored; openly acknowledging their existence could increase the desire of Arab states to develop a countervailing threat. Pakistan and India have been hit with sanctions barring certain technology sales, economic aid and loans from the World Bank or International Monetary Fund.

Some diplomats feel the spread of nuclear weapons is inevitable. One former Defense Department official notes that all arms control efforts throughout history have failed, starting with a Vatican-sponsored conference in the 12th century to ban production of the crossbow, an import from China that could pierce the armor of European nobles. "There's a certain arrogance to say that you can stop the spread of technology," the official said.

But others believe negotiations still can contain the most lethal weapons, coax India and Pakistan into observing the nuclear test ban and international inspection regimes, and further reduce the stockpiles of the major powers.

"Calling it a regime gave it a sense of being an iron castle, which never existed," said Frank Wisner, a former ambassador to India and Egypt who tried to persuade Russia to cut off aid to Iran's nuclear power program. "But the nonproliferation regimes still establish norms of behavior. They are like traffic laws; people still speed."

Wisner says it is more urgent to defuse the problems that drive countries to seek such devices. Better to engage North Korea, mediate the Indian-Pakistani dispute over Kashmir, resolve the Israeli-Palestinian problem, or figure out what Iran sees as threats to its national security, he says.

"Ballistic missiles are the symptom, not the problem," says Krepon of the Stimson Center.

Staff writer Thomas W. Lippman contributed to this report.