A U.S. scientific consortium partly funded by the military is negotiating to buy an advanced Soviet nuclear reactor intended for use in space, a deal that would constitute one of the first high-technology transfers between the two nations, U.S. officials said yesterday.

But independent experts differed sharply on the scientific significance of the purchase, with several describing it as in part a political effort to generate publicity about Soviet accomplishments that will aid the ailing U.S. space reactor effort.

The U.S. purchasing consortium includes two of the principal U.S. scientific laboratories working on nuclear and space weapons for the government, and some of its funds would come from the Air Force, the Energy Department, and the Strategic Defense Initiative Organization (SDIO), several officials said.

SDIO has been trying to develop a defense against Soviet missiles, and needs compact power sources for advanced satellites.

The United States, which last orbited a nuclear reactor in 1965, is developing a modern system for potential military applications, but the program has encountered technical problems and remains years away from completion. Its design is substantially different from the Soviet model, accounting for some of the U.S. interest.

"This would be the first of its kind of these high-tech transfers," said Richard Verga, the director of "key technologies" for SDIO.

Describing himself as the chief proponent of the idea, Verga said the aim was to "jump-start" a similar reactor development program by borrowing the best features of the Soviet system. He said such a reactor could be used in both military and civilian U.S. space applications, serving as a power supply for surveillance radars, lunar bases, satellite tugs, planetary probes, and manufacturing plants.

However, Richard Bohl, a technical program manager at the Los Alamos National Laboratory, said the Soviet Topaz II reactor appeared to be "a somewhat old design" more suited to Soviet than U.S. applications. Bohl said he inspected the Topaz II at a scientific conference in Albuquerque, N.M. yesterday.

Referring to an article about the purchase in yesterday's New York Times, Bohl said there was a "strong possibility" that publicity could rejuvenate the U.S. space nuclear power program. He said the purchase had as much political as scientific value.

Stephen Aftergood, an expert on space reactors at the Federation of American Scientists here, said "the technology frankly is of limited interest. I do not anticipate us having a great deal of use for one of these. There are {technical} controversies and safety concerns that may mitigate against them."

The proposed purchaseis nonetheless "remarkable because it is a breakthrough in international cooperation and commerce," he said.

Topaz II measures 13 feet tall and 5 feet in diameter, and is capable of generating 6,000 watts of electricity, several officials said. It has never flown in space, but is a variant of two Soviet reactors orbited in 1987 and 1988 and shut down after operating less than a year.

All Soviet nuclear reactors in space were shut down in 1988 after several fell from their orbits and dispersed radioactive materials in the upper atmosphere or on earth.

Verga said negotiations with the Soviets on the purchase price and terms are continuing, but it will likely cost less than $10 million. Besides the laboratory at Los Alamos, N.M., the consortium includes Sandia National Laboratories in Albuquerque and the University of New Mexico.