The Swiss government may not yet recognize it as a possibility and Pakistan's ruler, Mohammed Zia ul-Haq, continues to deny it, but most Western experts agree that Pakistan has been working flat out since the early 1970s to develop what former Pakistan president Zulfiqar Ali Bhutto called the first "Islamic bomb."

U.S. experts point to an abundance of evidence: intelligence reports, photographs of construction of an unmistakable uranium enrichment plant at Kahuta, and statements by Bhutto before he was deposed by Zia and executed.

The United States believes it will still take several years for Pakistan to finish the enrichment plant and produce suitable nuclear material for bombs, but they fear the process has become almost irreversible.

U.S. officials are studying closely a recent British Broadcasting Corp. television report on the Pakistan nuclear program that quoted anonymous Pakistani government sources who said Libyan ruler Muammar Qaddafi made an agreement with Bhutto in 1974, after a year of secret negotiations, to finance Pakistan's nuclear weapons program in exchange for Libyan access to its techology.

The BBC's Pakistani sources said a total of $4 billion in Libyan aid was discussed and that at least several hundred millions of dollars was sent by Libya to Pakistan in cash in 1975 and 1976.

Pakistan, like India, has refused to sign the Nuclear Nonproliferation Treaty or to allow the International Atomic Energy Agency to monitor its nuclear energy program to safeguard against the development of nuclear weapons. Some foreigners, including journalists, who have ventured too near Pakistan's nuclear installations or the homes of its nuclear scientists have been beaten.

From the beginning Pakistan's drive to develop an "Islamic bomb" has been a case history of the growing futility of international efforts to control the spread of nuclear weapons.

The United States, the Soviet Union, China, France, and Britain all have nuclear arsenals, including U.S.-owned NATO warheads and Soviet-controlled Warsaw Pact weapons deployed on the soil of numerous allied nations.

India has demonstrated its capability to make a bomb and Israel also is widely believed to be able to do so. South Africa, Argentina and Brazil are among a clutch of other nations which have much of the technology to build a bomb in the future.

Pakistan first sought openly to buy a French plant to reprocess uranium used in ordinary nuclear reactors and separate out plutonium that could be exploded in nuclear weapons. A major diplomatic campaign by the Ford and Carter administrations, which included considerable pressure on the French government and a brief cutoff of U.S. economic and military aid to Pakistan, stopped the project.

By the time the French government terminated the contract between Pakistan and the French firm SGN, partly owned by the French government, Pakistan had received most of the plant's blueprints but little of its sensitive equipment.

Nonproliferation experts fear that Pakistan could still try to build the plant from the French plans with components bought from a variety of countries exporting nuclear techology, or that Pakistan may be building a less sophisticated and costly reprocessing plant as India did.

Pakistan will have available for reprocessing used nuclear fuel containing plutonium from its nuclear power plant reactor at Karachi. Pakistan's atomic energy chairman, Munir Ahmad Khan, announced Aug. 31 that fuel for the Karachi reactor is being manufactured from uranium at another plant built at Chasma by SGN, which also has helped carry out quality control at the plant.

The French government had made an agreement with SGN to allow it to help finish and start up the Chasma plant so long as it did not provide "sensitive" technology that could directly lead to nuclear weapons development.

But in 1978, just as Washington had decided to restore U.S. aid to Pakistan, it was alerted by British diplomats to evidence that Pakistan was trying to develop the capability to produce weapons-grade nuclear material in another way: by the gas centrifuge process for enriching uranium.

U.S. experts found that Pakistan was clandestinely buying components for the centrifuge process -- sometimes through dummy companies coordinated by Pakistani diplomats in Europe -- from nuclear technology firms in the United States, Britian, West Germany, Switzerland and other countries.

Washington again cut off aid to Pakistan in Marach 1979. U.S. experts also began closely tracking international trade in nuclear technology to discover exports to Pakistan that might be used for developing the gas centrifuge enrichment process.

"These transfers to Pakistan have been basically nonsensitive technology that could or could not be used as components in nuclear weapons development and may or may not be covered by international agreements or national export laws," said one U.S. official, who would not discuss specific exporting countries by name.

"But we believe each government can make an effort to discourage the sale of these items if you know what they're going to be used for. They are sophisticated items of heavy equipment.

"Some countries didn't know or were lax and bureaucratically inept," the U.S. official said. "But some others knew what was happening and allowed it to go ahead for political or commercial reasons."