After his proposal to erect a 22-story glass-and-steel tower atop a Madison Avenue low-rise was criticized sharply yesterday by the Landmarks Preservation Commission, developer Aby Rosen told The New York Sun that he will alter the plans for an addition to the Upper East Side building.

“We’re going to change the way the building looks completely,” Mr. Rosen said, after a hearing in which commissioners asked the developer to scale back his plans to build a luxury residential tower above the six-story Parke-Bernet Gallery building. The commission stopped short, however, of voting to totally reject the building proposal.

Mr. Rosen said he and his architect, Lord Norman Foster, might propose a shorter building on a wider footprint atop 980 Madison Avenue, between East 76th and East 77th streets. “You can’t just take a tower and cut it down, but we can obviously go back to the drawing board and make the building look different — and that’s what we’re going to do,” the developer said in an interview.

Renderings of the sleek cylindrical structure were made public in October. Since then, the proposal has captured the attention of the neighborhood, where its proponents tout the aesthetics of the design and say it would enliven the neighborhood. Project opponents say a contemporary tower is out of place in a historic district.

Mr. Rosen purchased the Parke-Bernet building two years ago for about $120 million. “As much as I’m unhappy that we can’t build that tower, I’m very happy that we can build there — and we will build there,” he said.

At yesterday’s meeting, which ended without a vote for approval or rejection, some commissioners said they would support a building addition of several stories. The hearing was held at the Surrogate courthouse on Chambers Street.

“The presence of the proposed tower would cause irreparable damage,” to the delicate balance of elegant low and midrise buildings along Madison Avenue on the Upper East Side, a commissioner, Stephen Byrns, said.

Another member of the commission, the Rev. Thomas Pike, said as a clergy member, he is an authority on marriage. “This marriage makes me nervous,” Rev. Pike said, of the union of low-rise and high-rise. “I just feel it would be more appropriate somewhere else.”

But one commissioner, Jan Hird Pokorny, said he would support the plan in its current form. During the hearing, he held up a photograph of the Leaning Tower of Pisa and an adjacent domed church, showing what he said was the successful juxtaposition of disparate architectural designs.

Mr. Rosen said the revised proposal would likely be a contemporary design, but that he would consider using masonry — in addition to glass — and changing the color of the structure from silver to champagne.

Lord Foster’s design is an “architectural masterpiece” that belongs on an undeveloped lot where the public could walk up to it and touch it, a commissioner, Joan Gerner, said. Ms. Gerner said she would consider an addition to the existing structure of “two or, maybe three stories,” but no more.

Another commissioner, Christopher Moore, said he would support a four- or five-story addition. Mr. Rosen said he thought he should be allowed to build to a height on par with the 14- or 15-story structures in the neighborhood.

A revised proposal must be presented in a public hearing before Community Board 8, before being resubmitted to the Landmarks Preservation Commission, a commission spokeswoman, Elisabeth de Bourbon, said. She said the commission, chaired by Robert Tierney, decided to postpone a vote in order to give the developer time to submit a “substantially altered plan.”

A member of a preservation group, Defenders of the Historic Upper East Side, Teri Slater, said she wished the commission yesterday had voted down Mr. Rosen’s plan, which she called “extreme for the location.”

“We shouldn’t even be talking about height or scale,” Ms. Slater, who attended the hearing, said. “We should be talking about what a historic district is supposed to be — and what is the contribution of low buildings inside these districts.”