Bruce Ratner is said to be considering a plan for his Atlantic Yards development in Downtown Brooklyn that could increase the number of new apartments while shrinking the amount of new office space. No exact figure has been determined, although a final plan should be decided in the next several months for the 21-acre, $2.5 billion complex, which would include a basketball arena for the New Jersey Nets.

“We are looking at a plan to see whether we should build more housing, and we are studying what the breakdown would be between condos and rentals,” the executive vice president of Forest City Ratner, Jim Stuckey, told The New York Sun yesterday.

“There is an overwhelming need for housing in Brooklyn,” he said.

A potential glut in the commercial office market, with the rezoning of Downtown Brooklyn, the rebuilding of Lower Manhattan, and the rezoning of the far West Side, has not been a factor in the decision to rethink the balance of commercial and residential units in the development, Mr. Stuckey said.

“Worries about the commercial market is not a factor in our decision to consider more residential units,” he said. “The need for more housing is the only factor.”

Under the current plan for Atlantic Yards, which has been public for over a year, half of the 4,500 units are to be market rate and half are to consist of middle-income and affordable units. Affordable units are for families of four with annual income between $18,840 and $31,400. Middle-income units are set aside for families of four with annual income ranging between $31,400 and $100,480. Some of the affordable units will be apartments for seniors and condominiums for first time owners.

If the housing units are increased, the new units will follow the same mixed-income divisions, Mr. Stuckey said.

The possible change was met with skepticism from the New York City chapter of the Association of Community Organizations for Reform Now, or Acorn, which has worked with Forest City Ratner on the affordable housing units at the Atlantic Yards development.

“Until we do a real plan and Forest City says we are actually going to have 1,000 more units, for example, I’m dealing with 4,500 units that I know about,” the nonprofit group’s executive director, Bertha Lewis, said. “I’m happy to hear they are considering more residential units, but I’ve been in the business for a long time, and I don’t like pie in the sky.”