U.S. intelligence has found no hard evidence the Soviet Union is developing a radar-evading stealth aircraft, indicating the United States may be more than 10 years ahead in this key weapons technology, U.S. officials say.

The U.S. Air Force is developing the B-2 stealth intercontinental bomber built of composite and other non-metallic materials to be virtually invisible to enemy radar and already has in operation a squadron of more than 50 stealth fighters.Officials, who commented in recent interviews on condition of anonymity, said U.S. intelligence has come up with "no hard data" that the Soviets have begun work on a specific stealth weapon, although both U.S. stealth aircraft programs were started in the mid-1970s.

The United States also has begun development of at least one other stealth weapon, a long-range stealth cruise missile.

The comments of the officials are the first to state specifically that the Soviets have not yet begun work on stealth weapons, although it has been hinted at in government documents.

The 1988 edition of Soviet Military Power released by the Pentagon in April said the Soviets have been developing for more than 10 years the technology and expertise needed "for production of advanced weapon systems incorporating leading-edge materials."

It added, "In the United States, however, exploitation of advantages in carbon-carbon composites, plastics, ceramics and ceramic matrix composites is already enabling production of superior military systems."