Two trade groups yesterday asked a federal judge to delay American Telephone & Telegraph's request for a review of a 1956 landmark consent decree with the government that bars the Bell System from offering unregulated communications services.

The Computer & Communications Industry Association and the National Burglar & Fire Alarm Association also asked U.S. District Judge Vincent Biunno, who sits in New Jersey, to designate the two groups as intervenors in the controversial case.

Three weeks ago, AT&T asked Biunno to review the consent decree, which ended a government antitrust suit, to determine whether the Bell System can provide unregulated telecommunications services, such as data processing. The major provision of the 25-year-old decree bars AT&T from providing such services.

Under a December Federal Communications decision, AT&T was authorized to provide such new services through a separate subsidiary. But that decision also is being challenged by CCIA and other organizations in an appeals court proceeding here.

In their filing yesterday, the two groups charged that AT&T's characterization of the New Jersey request as a "narrow application for emergency relief" is "grossly inaccurate."

"The relief sought by AT&T would have the practical consequence of effecting a major modification of the terms" of that decree, the trade groups said. The two groups said the requests delay -- from April to June -- was needed because of the importance of the issues in the case and because of pending FCC and court matters.