Washington's top transportation official yesterday said he opposes the National Park Service's plan to permanently close a central section of Rock Creek Park to through traffic beginning in 1985.

Thomas Downs, D.C. director of public works and transportation, called Park Service officials this week to protest the plan. A Park Service spokesman said the agency has received many protests since it proposed traffic restrictions for the park last week.

Downs said yesterday he supports Park Service efforts to make Rock Creek park "a more enjoyable place" and might even support permanent road closings in the more distant future. But he called it premature to announce a 1985 closing.

"I'm opposed to making it a permanent regulation now," Downs said.

Downs said the Park Service should proceed slowly and should try experimental closings, first in non-rush hours, before permanent actions are taken.

Downs said he supports all of the other Rock Creek changes proposed by the Park Service to go into effect May 1, including closing one lane of Beach Drive between Joyce and Broad Branch roads during rush hours. This would permit bicyclists and joggers in the lightly used or "counterflow" lane, which only about 250 cars now use during rush hour.

This is the section of Beach Drive proposed for permanent closing in 1985. About 2,500 commuters and a total of about 4,000 to 5,000 motorists now use this section each day. More than 20,000 motorists, most of them commuters, daily use the southern sections of Rock Creek Park near the Kennedy Center.

The Park Service will hold an all-day open house to discuss the plan March 23 (7 a.m. to 9 p.m. at the Rock Creek Nature Center at Glover and Military roads) and will accept written comment until April 15.