The $23 million Lafayette Centre office and retail complex in midtown, under construction for two years, will open next month.

Located at 1120 20th St. NW., the 325,000-square-foot building, the first of the complex, rises 10 stories and includes a central atrium and plaza which will be surrounded by shops.

American Telephone and Telegrph will be the largest tenant in the brick complex designed by the Welton Becket architectural firm. Other major tenants include Union Pacific Corp., Paine, Webber, Jackson and Curtis stock brokerage, Federal Publications Inc. and two law firms -- Jackson, Campbell & Parkinson and Wender, Murase & White.

Almost one half of the 60,000 square feet of retail space is leased, according to E.M. Sleeker, executive vice president of Farr, Jewett & Associates, leasing agent and also partner with automobile dealer Jack Pohanka in the development of the complex.

Two more buildings are planned for the mid-block site that runs through to 21st Street. When completed, the complex will contain total of 750,000 square feet of space.

Sleeker said that various stores, a restaurant and an English pub will occupy space in the first building that is marked by three four-story arches on 20th Street. A 19-foot-high bronze sculpture by Barry Johnson will be placed under the middle arch.

Turner Construction Co. is the general contractor for the project, which is being constructed on one of the largest downtown sites assembled recently for a commercial center. Pohanka Oldsmobile formerly occupied part of the site.