The Montgomery County Council has tentatively agreed not to extend water and sewer services to the Rockwood Girl Scout National Center in the Potomac area until the master plan governing development of the area is formally approved.

The council is expected to make a final decision Aug. 15 on whether to delay the extension, said Margaret Stanley, planner for the county Office of Environmental planning.

The Girl Scouts of America and a development firm, which has contracted to buy the property from the Girl Scouts, had requested the extension. The developer, Berger-Berman Builders, Inc., plans to build up to 180 homes on the 93-acre tract at 11001 MacArthur Blvd., one of the few remaining wooded parcels of land in the Potomac area.

Stanley said the council decision was based on the need to have water and sewer services conform with the timing of the development and with existing sewer and public services for the area.

"The council requested a thorough examinaion of zoning patterns in this area of Potomac," she said, adding that the council was concerned "about all the input and the possible dense development of the land."

The decision, which was made at a recent work session, agrees with a recommendation by County Executive James P. Gleason to delay the extension until the master plan is approved. According to Lee Cunningham, planning coordinator with the Maryland National-Capital Park and Planning Commission, the plan is expected to be formally adopted in September 1979.

Stephen Blocher, an attorney for both the Girl Scouts and Berger-Berman, said no action has been taken by either party since the council reached its tentative decision.

According to Daniel French, director of national properties for the Girl Scouts, the council decision "will not alter the sale of the land. We are reviewing the situation at a higher level to determine what will happen."

The Rescue Rockwood Committee, a citizens group opposed to the sale, is working to prevent the development, because they say the land is invaluable and should be preserved as intended by donor Carolyn G. Caughey, a Washington socialite who willed the land to the Girl Scouts in 1936.

Anna Lopez, a member of the committee, said the council action was a "step in the right direction, but we are still going to bring suit against the Girl Scouts. We can't stop and take a breath because nothing has been settled - this is just a delay."