Garfinckel's, the Washington specialty store company, is conducting negotiatons that could lead to the opening of a new brach store in Georgetown.

Informed sources said yesterday that the local retailer, a division of Garfinckel, Brooks Brothers, Miller & Rhodas, is studying a proposed mall at 3222 M Street NW as the site for a new store.

William C. Detwiler, president of the Garfinckel division, said last night that negotiations have been "very, very preliminary" and that any discussion of the Georgetown site is "premature."

Garfinckel's now operates seven major stores and two hotel shops in the Washington area and the firm has been seeking to expand into the Chevy Chase-Friendship Heights area, where a proposed store next door to Woodward & Lothrop has been blocked by a zoning dispute.

Retail sources said new pressure on Garfinckel's to open more stores has been added by the arrival late last year of Bloomingdale's, a New York fashion-oriented department store that plans to open its second area store on Rochville Pike in March.

Garfinckel's itself completed major remodelings last year at its Montgomery Mall and Tysons Corner stores.

The retail mall being proposed for Georgetown is called Georgetown Square and sources said current plants are for the complex to open late next year or in 1979. The large site originally housed the horse-car barn for the D. C. transit business.

When area bus companies were taken over several years ago, a subsidiary of O. Roy Chalk's D.C. Transit System, Inc., retained ownership of the M Street property as well as an adjacent former power station in the back, along the C&O Canal. In 1972, the properties were assessed at more than $4.5 million.