The Americ an Speech-Language-Hearing Association and a Boston-based development firm have negotiated a tentative agreement under which a Montgomery County-owned arts center would get $570,000 for support of the association's hotly debated plan to build an office park at its Bethesda headquarters.

While the agreement is not yet final, the association and developers Spaulding & Slye tentatively have agreed to give the Strathmore Hall Foundation $75,000 and $495,000, respectively, if the developer gets appropriate rezoning and is permitted to build an access road through the foundation's property.

The arrangement has added fuel to the fight between the association, which wants to build four office buildings on most of the 11 acres surrounding its headquarters, and nearby residents.

"The issue here is an ethical one," said Sarah Clark, a member of the Garrett Park Citizens Association, which is fighting the proposed development. "If Strathmore Hall Arts Center is a quasi-public organization with ties to the county, is it ethical for them to lobby the county?"

Eliot Pfanstiehl, director of the foundation, said that the $570,000 the center would receive would be given largely for allowing the developer to build a road to Tuckerman Lane across the Strathmore Hall property, as well as in recognition of its support for the office project.

The foundation would use the payment either for additional arts programs or as seed money to build a theater, Pfanstiehl said. He added that the proposal is expected to come before the foundation's board of directors within the month.

Alton Fryer, a vice president with Spaulding & Slye, said that the proposed road would give the office complex two routes to Rockville Pike -- one on either side of the semi-circular Tuckerman Lane. It also would provide easier access to the Grosvenor Metro Station, he said.

Since the foundation's property is owned by the county, the road plan must be approved by the County Council, officials said.

The 20,000-member association wants to develop up to 350,000 square feet of office space and lease it to other groups in order to generate income for its programs, Executive Director Frederick Spahr said. The association represents practitioners who work with individuals whose speech, hearing or use of language is impaired.

The plan calls for a 1,000-car underground parking lot, which, under terms of the agreement, the foundation would be allowed to use on nights and weekends.

Although the area is zoned residential, the association's headquarters at Rockville Pike and Strathmore Avenue is next to three other institutions: Georgetown Preparatory School, the Academy of the Holy Cross and Strathmore Hall.

All of the institutions are located near the Grosvenor Metro Station and are considered prime sites for development, county planners say.

Members of several area civic groups and officials with the town of Garrett Park, a small municipality with a post office and 350 homes -- all of which are on the National Register of Historic Places -- fear that a rezoning of the property from residential to commercial would set a precedent that ultimately could change the character of the area.

Opponents also are objecting to the extra traffic that they say will spill from the development onto Strathmore Avenue, a two-lane residential street that doubles as the town's main thoroughfare.

A commercial rezoning would be contrary to the county master plan, opponents said, and would endanger one of the last large tracts of open land along the heavily developed Rockville Pike corridor.

The association, without citizen opposition, built its 40,000-square-foot headquarters in the mid-1970s under a special exception to county zoning laws that permits nonprofit, philanthropic organizations in residential areas.

The Montgomery County Planning Board is scheduled to consider the proposed rezoning on August 8.