The United States should take a more focused and flexible approach to export controls on computers, especially since the existing curbs on many components and systems have become virtually unenforceable, according to a scientific advisory panel.

It urged that the administration concentrate instead on striving - together with its NATO allies and Japan - to control leakage to the Soviet bloc of militarily valuable supercomputers and the most advanced computer manufacturing processes."The United States cannot afford to be complacent about its computer technology strengths or base export control decisions on an assumption of an invincible lead," said the National Research Council report, prepared at the request of the State Department.

It noted that "as the computer market becomes increasingly global, U.S. firms face increasing foreign competition, mostly from firms operating with fewer export barriers under the same CoCom guidelines."

CoCom is the Coordinating Committee for Multilateral Export Controls, comprising the United States, Japan and all NATO countries except Iceland.

The report contended that "tighter U.S. controls may reflect the absence of a fully effective multilateral control effort, but there is a risk that in the computer area, the United States may lock the proverbial barn door after the horse has escaped."

Preparing the assessment was a 17-member committee led by Seymour E. Goodman, professor of management information systems and policy at the University of Arizona, Tucson.

The National Research Council is the principal operating agency of the National Academies of Sciences and Engineering.

The report concluded that "current technological progress will make controls harder to enforce, and technological and market developments combine to make a case for a more focused and flexible control process."

Increasingly powerful computer hardware and software, it said, are in effect becoming commodities in world trade.

"Commodity products are available in high volume and at low cost, they may be available in multiple and substitutable forms, and they tend to be small and easy to transport," it said. "These attributes make commodities vital to the economic health of the computer industry, but also effectively uncontrollable."

The report recommended that the United States publish a list of computer technologies that are commodities. The government should then promulgate a policy exempting such commodities from export controls, at least for trade among CoCom nations.

On the other hand, it said, the State Department should work with other agencies to focus export control efforts on "computer technologies of compelling military importance" that could enable Soviet bloc countries to make substantial gains in their technology base.

In particular, the report cited advanced chip fabrication lines, supercomputers and other high-performance computing systems, computer-aided design systems, and magnetic and magneto-optical materials.

The study also said the United States should promote the integration of key newly industrializing countries - including Singapore, Hong Kong, Taiwan and South Korea - into the CoCom control program.

"Unless these countries are part of an effective multilateral control effort, their role as potential suppliers of computer technology to CMEA countries will grow," it said, referring to the Council for Mutual Economic Assistance, the Soviet bloc's common market.

The report said software should be divided into three main classes for control purposes.

"Software with a compelling and direct military importance should be tightly controlled; some degree of control should be provided for software tools that could build software in the first class; but other software should be traded freely among CoCom nations," it said.