One of the AT&T Corporation's sweetest victories last year -- a multibillion-dollar agreement with the Bell Atlantic Corporation to build an interactive video network that would reach eight million homes -- is about to go sour.

Bell Atlantic will announce on Thursday that it has dropped AT&T as the "systems integrator" supervising the gigantic project in favor of handling the job itself. The decision follows disputes between the companies over pricing and control.

It is a big blow for AT&T, which has been marketing itself as the company to orchestrate the design and construction of communications networks that will let customers order movies with a click of a remote-control device and send or receive huge amounts of data at high speed.

Bell Atlantic, which is based in Philadelphia and operates local phone services from New Jersey to Virginia, is one of the most aggressive of the regional Bell companies about expanding into video services, planning to spend about $5 billion in the next five years on this project. AT&T would have been similar to a general contractor, supplying much of the equipment itself while coordinating scores of other vendors.

But after the two companies signed a letter of intent in May, they became embroiled in disputes over the precise terms of the contract. Bell Atlantic executives have been frustrated by what they called AT&T's sluggishness in teaming with other key contractors -- particularly the General Instrument Corporation, which will supply digital-compression technology and set-top controllers for TV sets.

Lawrence T. Babbio, vice chairman of Bell Atlantic, said today that the company should control the project more directly.

"If you hire a general contractor to build your kitchen, you don't ever get to know how to build a kitchen," he said. "All you get in the end is the ability to use the kitchen."

AT&T executives tried to put the best face on the situation. "We have had a longstanding and very profitable relationship with Bell Atlantic, and we are sure that will continue," said Carly Fiorini, president of the North American division of AT&T Network Systems. "Bell Atlantic as systems integrator will continue to look for the best technology in the marketplace, and we will continue to look like a very strong competitor."

Mr. Babbio said Bell Atlantic would continue to buy much of its equipment from AT&T. Still, the move almost certainly means that AT&T will sell less equipment to Bell Atlantic than it would have were it making the purchasing decisions.

Several issues of control, not all dealing directly with the video network, led to the dropping of AT&T, Bell Atlantic executives said today.

AT&T, the nation's biggest long-distance carrier, is pushing into markets now controlled by the Bell companies like short-haul long-distance calls between nearby cities. Just last week, Bell Atlantic sued AT&T in New Jersey, accusing it of deceptive promotions on such calls -- a charge AT&T denies. Bell Atlantic also went to court last year, seeking unsuccessfully to block AT&T from buying McCaw Cellular Communications. Some Bell Atlantic executives said they wanted to avoid exposing themselves to further dependence on AT&T for its multimedia networks.

Bell Atlantic's project is behind schedule. The company had hoped to be wiring 100,000 homes a month by late this year; now it hopes to reach that goal by the summer of 1996.