WASHINGTON--The State Department said tonight it was without "legal authority" to prevent the sale to foreign powers of about 90 per cent of this nation's radar material.

It made this assertion in a statement as a Senate Judiciary subcommittee summoned its first witness to testify tomorrow at hearings on legislation to prevent the sale, gift, or loan to any foreign power of any radar of electronic equipment or plans.

The committee is inquiring into reports that certain American firms, with State Department consent, are negotiating with an unnamed foreign power, believed to be Russia, to provide them with the know-how on radar and other materials used in the war.