Although renowned for its seemingly endless string of fast-food restaurants, automobile dealerships and discount stores, Rockville Pike is fast becoming home to a growing number of hotel and office buildings.

Too fast in the eyes of city fathers and mothers, who last summer unexpectedly imposed a temporary building moratorium along the pike and, in action this week, gave preliminary approval to strict new limits on commercial developments there.

The City Council directed the planning staff to draw up an amendment to the city master plan that would reduce by a third the current maximum density allowed in commercial development along the heavily congested pike.

The measure would reduce the size of new buildings by reducing the maximum allowable floor space by one-third in commercial developments along the 1.5-mile stretch in Rockville between Twinbrook Parkway and Veirs Mill Road.

About 75 percent of that area is zoned for commercial development.

Rockville planners and an advisory group made up of Rockville Pike property owners and nearby residents recommended the "downzoning" last month as a way to lift the moratorium -- which expires April 2 -- and to protect the pike against future traffic gridlock.

The proposal calls for an "optional method of development," under which developers could build to maximum levels if they include certain public amenities, such as devoting spaces for landscaping or works of art.

The recommended reduction is expected to be approved by the City Council this month.

"I think it's the first step to bring maximum commercial development in line with what it should be," City Planning Director James M. Davis said of the proposed reduction.

"This is a negotiated consensus between the city staff, who wanted more reduction, and property owners, who wanted less reduction."

Davis attributed the recent surge in office building construction to several factors: the opening of the Metro subway, rising land costs that have forced developers to build more intensely, and an overall change in the character of the Rockville Pike corridor from a suburban main street to a more urban environ.

The largest ongoing construction projects, begun before the moratorium, include Jefferson Plaza at the pike and Veirs Mill Road, the Twinbrook Metro Plaza at Twinbrook Parkway, the Barlow building at Bouic Avenue and a 420-unit housing complex south of the 1776 Plaza.

The Montrose Civic Association, like other neighborhood groups adjacent to the pike, strongly supports the recommended reduction.

"Because of our location, and our dependence on the neighboring retail stores, we feel threatned by the impact of both the increased traffic and the new development along Rockville Pike," said Charlotte Joseph, president of the Montrose Civic Association and an advisory committee member.

Though most of the 20 committee members support the reduction -- according to its chairman, Rockville lawyer Joseph A. Lynott -- a handful of property owners oppose it.

Lowell E. Baier, president of Baier Properties and owner of the Wintergreen and Jefferson plazas on Rockville Pike, called the council's decision to impose the moratorium "insular" and the proposed downzoning "premature."

"Had they looked beyond the city limits, they would have recognized that the Rockville Pike market place starts at White Flint," Baier said. "They might have found out that there's enough going on out there that would forestall the imminent overbuilding they are anticipating."

The city's portion of Rockville Pike carries 2.7 million square feet of commercial space, including 1.7 million square feet of retail space and 568,000 square feet in office space, Davis said.

Planners have forecast up to 3.4 million square feet of commercial development along the pike by 1990, including 1.8 million square feet in retail space and 1.2 million in office space.