A multi-national corporation, which Montgomery County officials refuse to identify, has taken serious steps toward building a regional headquarters in Bethesda on five acres of land the firm now is negotiating to buy from the Martin-Marietta Corporation.

County's officials say the corporation is well-known, and two knowledgeable sources in the county speculated that it is General Motors. However, A.T. Hastings, director of real estate and property management for GM, said, "We did look at that site before Christmas, but we really don't have any plans to buy it."

He added that GM is interested in three other sites in Montgomery County for possible future location.

Although Martin-Marietta officials have confirmed that negotiations are in progress for the sale of the five acres, they have declined to identify the firm that is attempting to buy the land.

The corporation would build its regional headquarters just northwest of Fernwood Road and Rockledge Drive, next to Martin-Marietta headquarters on Rockledge Drive.

James Simpson, general counsel for Martin-Marietta, said the two firms had not agreed on a price for the land, and characterized the negotiations as up in the air.

"There's a considerable gap between the offer they've making and what we're willing to take," he said.

In addition to the firm negotiating for the Martin-Marietta land, two other large companies are seriously considering establishing offices in the county, according to James Giegerich, director of the Montgomery Office of Economic and Agricultural Development.

One firm is a "home-bred Montgomery County corporation that will expand," said Giegerich, who added that the planned offices will be a "big, big building - about 400,000 square feet."

The other company is "in the last throes of selection" of a site, he said. Giegerich refused to identify either firm.

New corporate offices would mean more tax revenues and more money for county businesses.

"The company (negotiating with Martin-Marietta) will generate substantial property tax revenues and some jobs," said Giegerich.

According to county officials and businessmen, Montgomery County would welcome such development.

Because of the benefits to the county economy and because of competition from Fairfax and Prince George's counties, which have been working aggressively to attract businesses, Montgomery County has begun to court some businesses itself - primarily prestigious, white-collar research and development firms.

The firm negotiating with Martin-Marietta already has second and third choices picked out in Rockville and Fairfax County, and Montgomery County officials are doing everything they can to ease the firm through the complexities of permits needed for water, sewer and other services.

At the firm's request, the county also has asked that a planned overpass across I-270 be eliminated from the county's master plan for development, and officials have carefully kept the unnamed company unnamed.

"We've lost Mobil Oil," said Giegerich referring to the company which recently located in Fairfax County. "We would like to see those kinds of companies here."

The land the firm has selected is part of about 400 acres bounded by I-270, Democracy Boulevard, Old Georgetown Road and the Capital Beltway. The area is commonly known as the Davis Tract - for farmer Floyd Davis who once owned all of it - and now is some of the most attractive, conveniently located and expensive land in the county.

Sometimes call the "Gold Coast," the Davis Tract has attracted IBM, Martin-Marietta, the Marriott Corporation (under construction) and Fairchild Industries, which have set up regional and national headquarters on land selling at premium prices. For instance, Marriott paid $3 million for a 33-acre parcel, according to one company official.

According to Simpson, of Martin-Marietta, the sale of the five acres hinges on whether or not the proposed overpass across I-270 is eliminated from the master plan for the area. "Nothing will transpire before that," he said.

The county planning board has recommended elimination of the overpass, which would link Westlake Terrace with Fernwood Road, but residents in the area want to keep it in the master plan. The County Council, which makes the final decision on the overpass, will hold a public hearing on the issue April 11.

Proponents of the overpass say it would remove some of the east-west traffic on Democracy Boulevard, which now spills off into bordering neighborhoods.

The firm negotiating with Martin-Marietta contends that the traffic generated by the overpass would spoil the "campus-like setting" the firm wants to create for its regional headquarters, according to Giegerich.

Giegerich said the firm has at least three offices, in Washington, Virginia and Baltimore, and the move to Montgomery County would be a consolidation of those offices. He described the company's proposed building as "set among trees, (in a) fully landscaped area. They describe it as in a "sylvan glen." That's the way their other headquarters are.

"(The building) will be at least as attractive as the Martin-Marietta building, which is very fine architecturally. It will be one of the finest architectural pieces in the county."