SPRINGFIELD, Mass. — Casino giant MGM Resorts International planned to formally unveil its plans for a “major entertainment complex” in Springfield, adding to the expected competition for the sole resort casino license in western Massachusetts.

The Las Vegas-based firm scheduled a formal announcement for Wednesday at the MassMutual Convention Center. No details were provided in advance, but MGM said architectural renderings of the project would be released and a tour given of the proposed site.

The company has been seeking a new location for a casino since announcing in March that it was abandoning plans to develop a resort in the rural town of Brimfield.

Western Massachusetts appears to be attracting the most vigorous competition for any of the three regional casino licenses allowed under the gambling law signed by Gov. Deval Patrick last year.

Other suitors include Ameristar Casinos, which in January purchased for $16 million a former industrial site off Interstate 91 in Springfield, and Mohegan Sun, which hopes to develop a resort casino in the town of Palmer.

Penn National Gaming and Hard Rock International have also expressed interest in pursuing a casino in the Springfield area, though neither firm has unveiled specific development plans. Peter Picknelly, chairman and chief executive of Peter Pan Bus Lines, has reportedly sought an option to buy property owned by the Republican newspaper of Springfield as part of a potential casino development plan.

Springfield Mayor Domenic Sarno was scheduled to hold private meetings with potential casino developers on Monday, according to Thomas Walsh, a spokesman for the mayor.

Sarno, who has yet to personally meet with any casino firms, was expected to brief developers on how the city planned to proceed and what it might look for from companies in exchange for hosting a casino, Walsh said Tuesday. The state casino law gives considerable power to municipal officials to negotiate host community agreements with potential developers.