The National Capital Planning Commission yesterday rejected a Tidal Basin site proposed for the Martin Luther King Jr. memorial and tabled for further study a decision on placing cellular telephone towers in Rock Creek Park.

But the panel, in a seven-hour meeting, approved the final design for the National Museum of the American Indian, which will be built at Third Street and Independence Avenue SW.

The 8 to 4 vote against placing the King memorial near the Franklin D. Roosevelt Memorial was a major setback for the Washington D.C. Martin Luther King Jr. Memorial Project Foundation, which already had received site approval from the Commission on Fine Arts.

Foundation officials said the vote will delay groundbreaking by at least a year and will force the foundation to begin the site selection and approval process all over again.

"We are extremely and deeply disappointed," memorial project manager John Carter said. "We went through the process, we did everything. We had looked at all the sites . . . and this is still the best site."

The foundation had mounted carefully orchestrated presentations to the Planning and the Fine Arts commissions and had participated in a task force made up of representatives from both commissions that had concluded the Tidal Basin site was the best for the King memorial. The foundation cannot go ahead with a design competition or raise funds until it has a site.

The King memorial site has been controversial. Initially, the foundation selected a site at the east end of Constitution Gardens, near the planned World War II Memorial, and received approval from the Planning Commission but was turned down by the Fine Arts Commission. The foundation then reconsidered two other sites that had been dismissed earlier and embraced the one on the Tidal Basin.

The Fine Arts Commission enthusiastically supported that choice last month. At that hearing, Planning Commission Executive Director Reginald Griffith testified that the staff of his commission would endorse the same site in an assessment to the board at yesterday's meeting. Griffith's testimony was taken as a sign that both boards would be in accord.

However, the Planning Commission members did not follow the staff recommendations. Commission member Margaret G. Vanderhye, a presidential appointee, spoke of her admiration for King and the work of the foundation, but said she opposed the site because it was on a flood plain and because of philosophical reasons.

"Philosophically, this site just doesn't work for me," she said. "This is not just a memorial to a great leader but a memorial to the people he led. . . . Whatever we do for a memorial, it should be a living entity, as is the Washington Monument."

Arrington Dixon, a mayoral appointee to the Planning Commission, said he objected to the adjoining polo field, the roadway through the site and the noise of airplanes overhead.

"There are too many things here that make me feel like this is the back of the bus," he said.

Griffith urged board members to look "not at what is there but what could be there. We recommended this site not because it was the back of the bus . . . but because we believed this could be designed in a way that is worthy of Dr. King."

Commission Chairman Harvey B. Gantt, a presidential appointee, was the last to speak, saying he would vote for the site not because he thought it was the best one but because the process of reaching the decision was fair.

"We want to move forward and not delay for a year or two, or maybe we will never do it," he said. "I didn't get the site I wanted, but I can't say this won't be a great site."

John Parsons, associate regional director of the National Park Service's National Capital Region, who voted in favor of the site, said the Park Service and the foundation would look again at alternative sites at each end of Constitution Gardens.

The commission voted to table, for a second time, a decision on placing cellular telephone towers in Rock Creek Park. The vote came after three hours of testimony.

Most of the 50 witnesses opposed the project, initiated by Bell Atlantic Mobile. Opponents pointed to concerns about migratory birds, the natural scenery and the possibility of many more towers to follow.

Those who spoke in support said the towers would not be obtrusive, are needed for public safety and pose no threat to the birds.

Commission Vice Chairman Patricia Elwood, a mayoral appointee, called for an outside study to help the commission make an informed decision.

Melissa Wojciak, who represented Rep. Dan Burton (R-Ind.) on the commission, objected to the tabling motion and urged members to support the towers. She warned that "others will go around you and the towers will be built. I will guarantee Congress would do that."

The commission voted 8 to 4, with one abstention, to table a decision.