Alexandria Hospital officials announced yesterday that despite longstanding residential opposition they plan to add doctors' offices, a cancer center and an outpatient surgical wing to the hospital.

A. George Cook, chairman of the Alexandria Health Services Corp., the parent company for the 414-bed hospital, said the plans still must be approved by the Alexandria Health Services Board and the City Council. He said he hoped the tentative proposals for the extensions, estimated to cost $12 million, would allay residents' fears that a new imposing structure will mar their affluent neighborhood.

"One of the biggest arguments against it is that it will be a commercial intrusion," Cook said. But, he said, the major extension, which will be built onto the front of the hospital at 4320 Seminary Rd., will be four stories and 108,000 square feet. The second addition will be one story and less than 5,000 square feet, according to the plans.

But former mayor Charles E. Beatley, a West End resident and leading spokesman against the expansion, immediately attacked the proposals.

"It reminds me of a supermarket for medical services," he said. "The increase in commercial activity will definitely be an intrusion."

For three decades, neighbors have been fighting the hospital's attempts to build doctors' offices and additional medical centers because of fears that traffic and parking problems would disrupt their quiet single-family neighborhood, Beatley said.

City officials and residents say they worry about declining property values and further commercialization in Seminary Hill, where homes are valued as high as $250,000.

"The residents are worried that if this is allowed, it might bring in more business," said City Council member Redella (Del) Pepper.

City officials approved construction of the hospital in the residential area in 1962, largely because it was nonprofit and originally had only 160 beds. Since then, however, the facility has almost tripled in size, and if the doctors' offices are permitted, the hospital complex will no longer be totally nonprofit.

"When it was built, it was not intended for commercial use," said Gant Redmon, president of the Seminary Hill Association, which represents about 2,000 families.

Hospital officials say the additions are necessary if the hospital is to stay afloat. It has the same financial troubles as hospitals nationally because of the federal health care cutbacks, and the spawning of numerous lower-cost outpatient facilities, they say.

Mayor James P. Moran Jr. said if hospital officials are determined to press ahead with their plans, the tension between the neighbors and the hospital is sure to erupt this spring during council hearings.