The chairman of the city’s Landmarks Preservation Commission is asking the administrators of St. Vincent’s Hospital and executives from the Rudin Management Company to rethink their billion-dollar plan for a new hospital and condominiums in Greenwich Village.

Although the 11-member commission took no official action at a hearing yesterday, the commission’s chairman, Robert Tierney, said the several hours of testimony and questioning of planners and hospital administrators will lead “to a necessary rethinking.” “You can reasonably infer from some of the lines of questioning that aspects of this proposal should be rethought and restudied,” Mr. Tierney said in an e-mail yesterday.

Another hearing on the St. Vincent’s expansion will be held in May.

St. Vincent’s and Rudin must gain approval from the landmarks commission to move forward with their plan to raze the modernist O’Toole Building on Seventh Avenue between 12th and 13th streets and replace it with a new 329-foot-tall hospital. St. Vincent’s would sell nine existing buildings to Rudin for $310 million, and the proceeds from the sale would go toward the new facility. Rudin would build 650,000 square feet of luxury housing, along with street-level retail space, underground parking, and medical office space. “We are waiting to hear the commission’s comments before we respond,” a spokesman for the project, Stefan Friedman, said. Yesterday, the commissioners focused their questions on a number of issues, including the height of the new hospital building. Urban planners hired by the developer explained that the current concave design requires an additional four floors to avoid a box-like structure that would have a more imposing presence at the street level.

The New York chapter of the American Institute of Architects spoke in favor of the plan, as did the local Chamber of Commerce. But of the 46 people who testified yesterday, about 40 spoke out in opposition to the height and density, as well as the precedent the plan would set for future large proposals in historic districts.

Responding to the commissioners’ questions, the chief executive officer of St. Vincent’s, Henry Amoroso, said health care in Manhattan would suffer if the plan were defeated and that this was the best funding option given the terms of the hospital’s recent Chapter 11 reorganization. St. Vincent’s emerged from bankruptcy protection last August after filing three years ago.