CHICAGO (AP) _ A major developer has announced plans to build a slender 125-story skyscraper that would tower over the current world's tallest building, and said it already has inquiries from prospective tenants.

Miglin-Beitler Developments Inc., a major developer of offices in Chicago and its suburbs, announced Monday it plans to build a 1,914-foot downtown skyscraper - nearly 400 feet taller than the 110-story Sears Tower, which rises 1,522 feet with its antenna and has been the tallest building since its completion in 1974.

Miglin-Beitler presented its plans to the city's planning department last week and hopes to get approval in time to start construction in December.

''J. Paul Beitler said four years ago when I joined the firm that he was going to build the world's tallest building,'' said Miglin Beitler spokesman Mark Jarasek. ''It is a dream every developer has.''

He said the company wouldn't identify any prospective tenants who have made inquiries ''until we get approval of the building from the city.''

However, renting all the space could be a problem. Sears, Roebuck and Co. announced last fall that it planned to sell Sears Tower and move its 6,000- worker Merchandise Group out of the building as part of a restructuring plan, opening up abundant office space in the city.

The proposed building, being designed by architect Cesar Pelli of New Haven, Conn., would be built on a one-acre parcel about three blocks from Sears Tower, Jarasek said.

It would contain 1.2 million square feet of office space, only about one- third the rentable space of the bulkier Sears Tower. It would contain two floors of retail space at its base, a third-floor mezzanine level, 10 stories of parking and a two-story health club.

It would be built with concrete ribbing reinforced by steel. The core of the building also would be concrete. The outer skin would be reflective glass and aluminum ribbing, Jarasek said.

Chicago Planning Commissioner David Mosena said he couldn't take an official position on the building until his department had a chance to study it.

''Tall buildings don't cause as many problems as bulky buildings, and in terms of square footage, it is not that great,'' Mosena said, adding the commission was collecting information on the likely impact on traffic congestion and pedestrian movement.

He said it could take three to six months for the commission to make its recommendation to the City Council.

Michael Gelick, a professor of architecture at the University of Illinois- Chicago, says the technology has existed for years to build a building with the height proposed by Miglin-Beitler.

But he said construction of required stairways, support columns and vertical shafts for wiring, air conditioning, elevators and the like ''wouldn't allow for efficient use of the floors.'' Gelick added that it would be more economically feasible to build two buildings of lower height side by side.