The National Park Service, acting largely at the behest of the security-conscious U.S. Secret Service and White House staff, announced plans yesterday to close East Executive Avenue permanently to public traffic.

The block-long street between the White House and the U.S. Treasury Building once was a popular shortcut for thousands of commuters, but it has been blocked by large concrete flower pots since March 1983. Most of it will be turned into a parklike promenade for pedestrians.

James McDaniel, the Park Service's associate regional director here, told the National Capital Planning Commission that the street, extending from Pennsylvania Avenue NW on the north to Alexander Hamilton Place on the south, will be torn up and replaced. The Park Service will widen the sidewalk next to the White House and build a service lane for a small number of delivery trucks and law enforcement vehicles that will be sandwiched between two strips of grass.

In addition, large, permanent gates will be erected at both ends of East Executive Avenue to create new barriers against would-be truck-bomb terrorists such as those that have attacked U.S. facilities in Lebanon. McDaniel said the sidewalk gates would almost always be open to pedestrians, but could be closed in an emergency. Gates at the ends of the service lane would remain closed except for use by authorized vehicles.

McDaniel said the construction work, expected to cost $1.5 million, will create an "esthetically pleasing entrance to the White House" for the thousands of visitors who line the street daily, waiting to enter the White House for brief tours.

While the street is torn up, the Secret Service also will be installing undisclosed security equipment at an additional cost.

The planning commission gave what it described as "very preliminary" approval to the plan, but said it wanted to review further the design of the gates, sidewalk and plantings when the Park Service completes work on the proposal in the next two months.

East Executive Avenue once handled 10,000 cars daily and served as one of the main north-south corridors for downtown Washington. It was closed last year because of construction of a new $771,000 security screening pavilion for White House visitors. White House staff members used the street for a parking lot for a while, but in the last year only law enforcement vehicles have been granted access, the Park Service said.

East Executive Avenue was not a part of the original White House design in 1791. It was built during the administration of Ulysses S. Grant in the 1870s to accommodate the public for visits to the White House.