The Defense Department said yesterday that all the military services are now assessing what secret communications the Soviet Union might have intercepted as a result of the alleged spy ring headed by John Anthony Walker Jr.

Spokesman Michael I. Burch, confirming The Washington Post's report yesterday that the Army as well as the Navy has established a damage-assessment team, said the Air Force also is "moving out" on the potential problem of compromised communications.

He said the services will review and possibly modify coding systems and procedures in hopes of foiling Soviet decoding efforts.

Observing that military services and government agencies use much the same sensitive communications systems, Burch said:

"As a result of the Walker case, the services are going back and looking at that point in time during which there may have been an exchange of information, there may have been communication. Once they do that, they will assess any possible damage that may have been done and what might have been compromised during that period.

"Independent of that, they're all reviewing the procedures by which they handle, transmit and receive classified information in hard copy and voice, handling and storing. The system is one which has built-in safeguards. One of the safeguards is continually changing."

Although Burch declined to elaborate, other sources said intelligence officials are particularly worried about the likelihood that the Walker ring gave the Soviets top-secret cards inserted into coding machines to code and decode sensitive messages.

Cryptographers are supposed to change the cards at the sending and receiving ends of secure communications links at least every day, and sometimes more often, officials said.

But, having enough of the key cards and knowledge of communications and coding hardware might have enabled Soviet specialists to break U.S. codes on sensitive messages, sources said.

Adm. James D. Watkins, chief of naval operations, said Tuesday that the Navy assumes that materials supplied by the Walker ring enabled the Soviets to break the Navy's supposedly "secure" voice and teletype communications. He said the Navy is changing the systems on an "accelerated basis" to minimize possible further compromise.

Other government officials said much of the communications and coding systems to which Watkins referred are used widely through the government, raising the possibility of widespread damage to U.S. security. Burch declined to discuss the possibility of compromising beyond the Defense Department.

He said the National Security Agency has "an interest in this" because of its responsibility for protecting U.S. coding systems and "attacking foreign communications."