The Federal Communications Commission is negotiating with the Justice Department to gain a full and firm say in the Justice Department's approval of American Telephone & Telegraph Co.'s landmark divestiture plan.

Otherwise, the FCC ultimately could reject several key aspects of the divestiture plan by refusing to give its required regulatory approval if the commission objects to the plan, a high-ranking FCC official indicated yesterday.

Among other things, the commission could refuse permission for AT&T or its affiliates to transfer facilities, to discontinue service or to construct new facilities.

"Down the road, we have to sign off on all of this. So it is in Justice's best interest to have our input now rather than later," said the FCC official, who met informally with reporters but declined to be quoted by name.

However, this official said, based on negotiations to date with Justice Department officials, "we have every expectation" that the FCC will have some input in approving the historic divestiture in which AT&T will spin off all of its local operating facilities at its 22 local operating companies.

The negotiations began shortly after the settlement was signed on Jan. 8 to end the government's seven-year-old antitrust suit against AT&T. Under the current terms of the settlement, only the Justice Department would have the authority to approve the details of the divestiture.

"We want to be able to have some input in the plan," the FCC official said.

On other matters, the official said the commission, having just last week approved low-power television, the first new television service in 20 years, will take action soon to introduce other new broadcasting services.

In June the FCC probably will approve a new service in which television programs are broadcast via satellite directly to a special receiver at the viewer's home, thereby bypassing the existing networks and local stations, the official said.

Additionally, the commission is about to consider a proposal to lift present restrictions that bar television networks from operating cable systems.