The National Capital Planning Commission yesterday unanimously chose a site on the Tidal Basin to honor Martin Luther King Jr., granting the slain civil rights leader a place of honor in one of the nation's most visited, and visible, open spaces.

The memorial will be built in a line between the Lincoln and Jefferson memorials and near the tribute to Franklin D. Roosevelt. With the decision, King becomes the only private individual elevated to such a distinction, his memorial soon to be a part of the nation's monumental core.

A jubilant John Carter, King memorial project manager, said after the vote that the foundation was ready to go on to the design phase.

"We are ready to launch our international design competition as of, well, as of today," he said, holding up a mailing tube that was addressed to one of the 80 people who had asked for competition information. He said that the deadline for entering the competition is May 1 and that organizers expect to hold an award gala event June 15.

Although the commission's vote in favor of the Tidal Basin site was never a sure thing, Carter said he wanted to be ready to move quickly if the vote was to approve that site, the one the Martin Luther King Jr. Memorial Project Foundation had embraced.

In July, when the commission voted against the Tidal Basin site in favor of a location on the Mall closer to the Lincoln Memorial, member Arrington Dixon said the Tidal Basin site was a "back of the bus" location, one not worthy of King.

The approved four-acre site is in an area frequented by tourists and is within the cherry blossom grove that attracts millions each spring.

Yesterday, Dixon said that he still had reservations about the choice but that there is "nothing we can do that would take away from the significance of King."

Commission Chairman Harvey B. Gantt had reluctantly voted for the Tidal Basin site in July, saying it was not the best choice but that the process was fair and it was time to move on. Yesterday, he was much more enthusiastic about his vote, saying the site was the right one. He pointed out that in an aerial photograph, the site was in a direct line between the Lincoln and Jefferson memorials, and close to the Roosevelt memorial.

"Dr. King needs his own site, one between [the] presidents whose words impacted this country in a profound way, as did his words 30 years ago," he said, noting that King is often associated with the Lincoln Memorial because of the March on Washington in 1963, when King gave his now famous "I Have a Dream" speech there.

Gantt said the 12 commission members "had been round and round" on the site issue. "Some have changed their minds and some prefer other sites, but we all believe he deserves a place of prominence. . . . Roosevelt and Jefferson are not back door."

Two of the three witnesses spoke against the site, suggesting more time was needed to consider other locations. The third, Stuart F. Feldman, said he had worked for 10 years to get Congress to approve a King memorial but he had hoped it would take the shape of two marble tablets with King's word inscribed on them and be located on the steps between the Lincoln Memorial and the Reflecting Pool.

Feldman had made the same suggestion at the July meeting. However, yesterday he said he was ready to support the commission's decision and would work actively to raise money for the memorial.