A federal arts commission renewed concerns yesterday about the design of a proposed memorial to the Rev. Martin Luther King Jr., saying it could obstruct views of the Tidal Basin and the Jefferson Memorial.

During its first review of the project in three years, the U.S. Commission of Fine Arts had the option of taking a preliminary vote on the design. Instead, commissioners chose to schedule a visit to the site in West Potomac Park and to hold further discussions with the designers.

Several commissioners expressed concerns about the architect's proposed creation of a narrow footbridge about 10 feet above the ground as well as a curving wall, saying the structures could block views of the water.

One commissioner, Elyn Zimmerman, a New York-based artist, questioned the originality of one aspect of the memorial, two granite rock formations divided by a footpath. She said the design resembled a sculpture, "Marabar," that she made more than 20 years ago and is in the plaza of the National Geographic Society.

Zimmerman's sculpture consists of two oversized granite forms divided by a narrow reflecting pool. As in the proposed King memorial, the rocks' interior walls are smooth.

Boris Dramov, one of the memorial's designers, said after the hearing that he had recently seen Zimmerman's sculpture and did not view it as similar to his team's conception. "They're very different. I don't know why there would be a concern," he said.

Ed Jackson, the project's executive architect, said that he is looking forward to further discussions with the commission and that he was heartened by the members' overall praise for the design.

The designers' presentation was their first to the panel since 2002, when commissioners expressed similar concerns. In response, the design team moved a rock formation, reduced the number of seating niches from 28 to 15 and introduced two 12-foot waterfalls.

As for the footbridge, Jackson said that it would not create an obstruction and that he thinks commissioners will agree once they visit the site with him. He said the bridge would create a narrow portal that would enhance the view of the Tidal Basin.

The memorial's foundation announced that filmmaker George Lucas has donated $1 million to the project. The foundation had previously raised $40 million for the project, which its leaders said will need $100 million to be completed.

It would sit on a four-acre triangular site in West Potomac Park, on the northwestern corner of the Tidal Basin, between the Jefferson Memorial and the steps of the Lincoln Memorial, where King delivered his "I Have a Dream" speech.

At the center of the site is a 28-foot-high rock structure, "Stone of Hope," which would feature an inscription and King's likeness on its facade.

The idea for a memorial was born in 1984, when George H. Sealey Jr., a retired Army major, pitched the idea to his fraternity, Alpha Phi Alpha, the nation's oldest black fraternity, of which King was a member.

The group endorsed the idea and spent the next 12 years seeking support on Capitol Hill. Congress approved the location in 1996.

Boris Dramov, one of the designers of the Martin Luther King Jr. memorial in West Potomac Park, talks to the Commission of Fine Arts. Design team members Ed Jackson, left, and Paul Devrouax listen to the presentation.A model shows the concept of the proposed Martin Luther King Jr. memorial, which would be in West Potomac Park.