Architect I. M. Pei, who will design the John F. Kennedy Memorial Library, explained in an interview last week why he wants to retain the option of having commercial buildings near the library.

Pei said he thought "support facilities"--such as souvenir shops, restaurants, and parking lots--would probably be necessary to help control the impact of the library on the Harvard Square area. The library will draw an estimated 750,000 visitors annually. Souvenir shops, Pei explained "would inevitably come Pei said he will discuss possible road and traffic-flow changes with city officials in another attempt to help reduce the library's impact on the city.

A state commission appointed to recommend a Massachusetts memorial to President Kennedy recentlyg suggested that the state cede six acres of the 12-acre Bennett St. MBTA Yards, across Boylston St. from Eliot House, to the federal government. The six acres would house the buildings directly connected with the library.

The commission recommended that the state hold most of the other six acres in reserve, perhaps as a site for a park or plaza. An acre or two would be sold to the Kennedy Library Corp. and resold to Harvard as a site for the proposed Institute of Politics, which will be connected with the library.

Pei had preferred that the state sell all the remaining acres to the Library Corp., part for sale to Harvard and the rest for commercial development, with the architecture controlled by him.

If the commission's recommendation becomes law, Pei would be prevented from building any commercial structures on the site.