Several nations that do not possess nuclear weapons "took important steps" toward acquiring the ability to build such bombs last year, according to a report yesterday by the Carnegie Endowment for International Peace.

The report says Pakistan "may have acquired the capability to manufacture nuclear arms" during the year, which it says could have grave consequences for regional stability. India, which detonated a nuclear "device" in 1974, is more likely to resume its testing program because of Pakistan's progress, the report maintains.

A similar rivalry between Argentina and Brazil also became more intense in the nuclear field last year, the report states, although neither nation is as far along as India or Pakistan. Iraq and Libya also continued their efforts to get the bomb, the report says.

"Nuclear proliferation involving these nations -- many of which have fought repeated wars with bordering states and have highly unstable governments -- presents a host of new and unpredictable dangers to world peace," the report concludes.

The 478-page report was written by Leonard S. Spector, a senior associate at the Carnegie endowment who served between 1978 and 1980 as chief counsel to the Senate energy and nuclear proliferation subcommittee. The project, which was supported by grants from the Carnegie Corp. of New York and the Rockefeller Brothers Fund, is intended to be the first in an annual series.

The report relies heavily on press accounts and does not appear to contain new disclosures of nuclear capability among what it calls "emerging nuclear weapons countries." It collects what it says is "disturbing" evidence that several nations continue to seek at least the "ambiguous" level of being able to assemble nuclear weapons quickly if they desire.

"And if more nations reach this level of nuclearization, there will be no guarantee that they will remain at this plateau or that still others will not be encouraged to follow their example," the report states.

Five nations openly possess nuclear weapons: the United States, the Soviet Union, Great Britain, France and China. Israel, South Africa and India are the "ambiguous" nations that are thought to possess weapons or the technology and materials to make them. Pakistan may have reached that level recently, the report states.

Argentina, Brazil, Iraq and Libya are thought to be further from joining the nuclear "club" but are pursuing efforts in that direction, according to the report. South Korea and Taiwan, which used to be included on most lists of potential nuclear powers, do not appear to be pressing forward, Spector said.

Spector said the Nuclear Nonproliferation Act has helped prevent the emerging nuclear nations from legally acquiring the materials and know-how they need. He said other supplier countries, including the Soviet Union, also have shown great responsibility in how they export materials.

"The bad news is they [the emerging countries] are continuing to have some success with these black market transfers," Spector said.