The United States has no clear military policy about how the nation might respond to a cyberattack on its communications, financial or power networks, a panel of scientists and policy advisers warned Wednesday, and the country needs to clarify both its offensive capabilities and how it would respond to such attacks.

The report, based on a three-year study by a panel assembled by the National Academy of Sciences, is the first major effort to look at the military use of computer technologies as weapons. The potential use of such technologies offensively has been widely discussed in recent years, and disruptions of communications systems and Web sites have become a standard occurrence in both political and military conflicts since 2000.

The report, titled “Technology, Policy, Law, and Ethics Regarding U.S. Acquisition and Use of Cyberattack Capabilities,” concludes that the veil of secrecy that has surrounded cyberwar planning is detrimental to the country’s military policy.

The report’s authors include Adm. William A. Owens, a former vice chairman of the joint chiefs of staff; William O. Studeman, former deputy director of the Central Intelligence Agency; and Walter B. Slocombe, former under secretary of defense for policy. Scientists and cyberspecialists on the panel included Richard L. Garwin, an I.B.M. physicist.