NEW YORK (AP) _ Rhone-Poulenc Rorer Inc. is making an aggressive new move into biotech research on some of medicine's most difficult diseases.

The French-owned drug company on Monday announced creation of a consortium of 14 companies and research groups that will explore gene and cell therapy treatments for cancer, heart and circulatory diseases, AIDS, Alzheimer's and other afflictions.

Rhone plans to spend $100 million in each of the next two years or about 15 percent of its total research and develoment budget on the project, which involves small biotech companies, U.S. and French research centers and companies already affiliated with Rhone-Poulenc Rorer.

While biotech affiliations are common, this is believed to be the largest such group. It brings together expertise in a variety of scientific specialties related to cell and gene therapies - emerging biological technologies that are still in the experimental stages.

In cell therapy, diseased cells are usually extracted from the body, then treated with nutrients or biological agents that might be too toxic to inject into the body. Once the cells are treated and healthy, they are multiplied in the lab, then injected back into the patient.

Gene therapy involves replacing defective or missing genes with functional genes. This can be done in the lab, similar to cell therapy, or by injecting the good genes into the body. A difficulty in this therapy is making sure the new genes are delivered to the affected organ or cells and getting them inside the cells to do their jobs. This is sometimes done using ''vectors'' which are a kind of dormant virus that can carry healthy genes created in the lab and ''infect'' them into diseased genes.

Rhone-Poulenc Rorer, based in Collegeville, Pa., is majority owned by the Paris-based chemical drug and chemical conglomerate Rhone-Poulenc SA.

While the company is already involved in biotech research, the consortium represents a major expansion, officials said.

The consortium's work will be managed by a new Rhone division, RPR Gencell, said Thierry Soursac, an RPR senior vice president who will head the venture. A committee made of representatives from each member will set research priorities and dole out work assignments.

Rhone-Poulenc Rorer will fund some of the research and coordination and will have marketing rights for any drugs that are produced. Each company or research group that participates in a drug's development will get a share oits revenues.

There will be a total of about 800 researchers, 150 of which will come from Rhone, said Soursac.

Soursac said expertise in cell and gene therapy is now spread widely among many biotech companies, many of which are struggling because their work only represents one piece of a larger puzzle.

Soursac sees them as similar to companies that make individual parts of a car. ''They're like bumper or headlight specialists, not builders of cars.''

Each of these therapies involve multiple steps and not all companies are exploring all the steps.

Biotech industry analysts said the alliance has promise.

''There is no way companies will be able to develop clinically significant and commercially feasible products based on cell and gene therapy without putting together a consortium like this,'' said Cynthia Robbin-Roth, editor- in-chief of Bioventure, a monthly Biotech industry newsletter published in San Mateo, Calif.

Arvind Desai, a drug industry analyst with the independent firm Mehta & Isley in New York, called it a ''grand design.''

''It depends on how, in reality, cell therapy works out and gene therapy works out and how efficacious and well-tolerated and safe these therapies are. The answer to that is not known.''

Desai doesn't expect to see any treatments from the consortium on the market until 1997 at the earliest.