Marriott Corp. is negotiating to buy up to a dozen Burger Chef fast-food restaurant locations in the Washington area, a company spokesman confirmed yesterday.

If the sale is consummated -- possibly by he end of year -- most of the Burger Chefs would be converted into units of the Roy Rogers fast-food business operated by Marriott.

Marriott, a Bethesda hotel, restaurant and airline catering company, already has 54 Roy Rogers locations in the metropolitan area. The addition of 12 restaurants would make the Marriott business the largest fast-food chain here.

The Marriott spokesman said one of the Burger Chefs may be converted into a Big Boy restaurant.

Marriott officials have told managers of area Burger Chefs that the Bethesda company wants to set up interviews with them about continuing in their current posts and that the same approach will apply to all employes. "We need all of them," the spokesman said.

Area Burger Chefs are operated under a franchise from the national company by Potomac Hamburgers Inc., a Northern Virginia company that is discussing sale of the units to Marriott. These are six Burger Chefs in the Maryland suburbs and four each in the District and Northern Virginia.

The possible sale of local Burger Chef units reflects increased cost pressures in the fast-food business, particularly for food prices and minimum wage increases. With more units over which to spread out overhead costs, such as advertising, individual restaurants are more profitable to operate.

Marriott officers revealed last week, in a presentation to securities analysts, that they are considering acquisitions as a method of future growth -- mostly in areas of current business.