Needed: new ideas to halt spread of nuclear weapons. Easing security concerns may be key to extending nuclear treaty

``What we badly need to stop nuclear weapons spreading are some new ideas. All you hear these days are ideas from the 1960s. . . .'' The spread of the weapons ``is driven not so much by competition as a sense of insecurity. . . . From the most powerful country to the weakest, there is a sense of vulnerability.''

These two comments were made here at a ``rehearsal'' conference for a major review of the landmark nuclear Non-Proliferation Treaty (NPT) of 1968. The review meeting of the treaty, which has now been signed by 128 countries, is scheduled to begin Aug. 27.

The first came from David Fischer, former director-general of the International Atomic Energy Agency (IAEA), a United Nations agency in Vienna which in part applies safeguards outlined in the NPT. It was echoed by other expert sources.

There was considerable interest in a Swedish proposal to double the number of IAEA inspectors, and to try to persuade Moscow and Washington to allow all their civilian nuclear plants to be inspected.

The Swedes see this as a step they hope will lead to a freeze on the production of nuclear weapons. The United States has offered to accept a Soviet inspector as part of an IAEA team to inspect civilian reactors. The Soviets, who are accepting an IAEA team for the first time later this year, will eventually accept a US inspector, sources report.

The second comment was from Prince Sadruddin Aga Khan, former United Nations high commissioner for refugees and candidate for UN Secretary-General.

He and Mr. Fischer spoke at the end of the three-day ``rehearsal'' conference organized by the prince's Bellerive Foundation. Other speakers agreed that easing security fears was the key to persuading the 45 countries that have not signed the NPT to join it.

Among the nonsigners are India (which exploded a nuclear device in 1974), Pakistan (which is on the verge of completing a bomb), Israel (believed to have had bombs for at least a decade), South Africa (also said to possess at least one bomb), Argentina, and Brazil.

North Korea is said to be interested in joing the nuclear club, according to the head of Britain's Social Democrats, David Owen, who felt the NPT was being steadily eroded. Dr. Owen said a complete test ban treaty was needed to persuade nonsigners to sign.

The last NPT review, in 1980, broke up because of third-world exasperation at the slow pace of disarmament. The NPT binds nuclear powers to ``pursue negotiations in good faith'' to stop the arms race, to disarm, and to produce a treaty on disarmament.

Lewis A. Dunn, assistant director of the US Arms Control and Disarmament Agency, told the Bellerive gathering: ``The highest priority now should be on radical reductions in existing nuclear arsenals.''

It was unlikely, he said, that any state would withdraw from the NPT in August. The US and the USSR had resumed missile talks. No country was known to have developed and detonated a nuclear device since India did in 1974, and 14 countries have signed since 1980.

As US and Soviet delegates at Bellerive blamed each other for the arms race, blunt exchanges erupted between US Assistant Defense Secretary Richard Perle and Soviet America-watcher Georgi Arbatov.

Notable at the Bellerive meeting was a feeling of what Prince Sadruddin called ``frustration'' over the continued superpower arms race, and a view that the US ``star wars'' nuclear shield program would only force the Soviets to build more warheads and launchers to penetrate it.

Nuclear states ``should not imagine that the review conference will be smooth,'' said a third-world ambassador. ``So far we have kept our powder dry. But we intend to speak out.''

The NPT itself expires in 1995.