The Defense Department this week issued one directive and prepared to issue a second that will clamp down on release of unclassified and previously available information about weapons and other military systems.

Pentagon officials said yesterday that the directives are intended to reduce the flow of militarily useful technology to the Soviet Union.

Critics said the directives are worded so broadly that they could also be used to restrict the flow of embarrassing information about weapons performance and other matters to journalists, watchdog groups and congressional aides.

"We're very concerned that what they're doing here is an expansion beyond what classification would allow and what Congress envisioned," Allan Adler, legislative counsel to the American Civil Liberties Union, said.

Adler said he is concerned, among other things, that one Pentagon document includes as "technical information" subject to new restrictions any information "which relates to research, development, engineering, test, evaluation, production, operation, use and maintenance of munitions and other military supplies and equipment."

"I can understand the concern," responded Dave Whitman, a security specialist in the Pentagon. "But this is really a system to aid the automatic release of this information to these classes of people on certain distribution lists . . . . To turn around and call it a withholding system is a distortion."

Whitman agreed that both directives are aimed at preventing disclosure of certain types of information. As an example, he cited the case of a "data broker," who applied under the Freedom of Information Act for all unclassified drawings of an advanced U.S. fighter jet and then sold the information to interested companies.

One directive, signed Tuesday by Deputy Defense Secretary William Howard Taft IV, essentially gives the Pentagon a new exemption on materials that must be released under the information act. It may now withhold any information that could not be sold abroad under the Arms Export Control Act.

Francis Sobieszczyk, assistant to the secretary of defense for scientific and technical information, said the directive closes a large loophole. Formerly, the Pentagon had no authority to withhold such sensitive information but, after it was in the public domain, the government had no authority to control its export.

The second directive establishes seven new categories for who may have access to unclassified technical information, such as "Defense Department only" or "Defense Department and certified contractors."