SPRINGFIELD, Mass. (AP) — Casino giant MGM Resorts International re-entered the Massachusetts casino sweepstakes on Wednesday with an ambitious $800 million plan for a resort entertainment complex in the heart of downtown Springfield.

The Las Vegas-based company announced during an elaborate event at the MassMutual Convention Center that the complex would be built on 10 acres heavily damaged by a tornado in June 2011.

The proposal includes a 250-room hotel, 89,000 square feet of gambling space and 70,000 square feet of retail and restaurant space.

‘‘We don’t want to build a box,’’ said Jim Murren, chairman and chief executive of MGM, which operates prominent Las Vegas properties including the Bellagio, MGM Grand and Mandalay Bay. ‘‘We want to build an urban environment.’’

MGM settled on the Springfield site after abandoning an initial plan to develop a resort casino in the rural town of Brimfield, citing insurmountable challenges associated with the remote site.

The company now faces a two-pronged competition — one to win the hearts of Springfield officials and residents, and the other to win the support of the five-member Massachusetts Gaming Commission, which ultimately will select among bidders for the sole western Massachusetts casino license under the state’s new gambling law. The law allows for up to three regional casinos in the state.

The western region — and Springfield in particular — appears to be attracting the most vigorous competition.

Ameristar Casinos has proposed a resort casino on a former industrial site off Interstate 91 in Springfield, and at least two other developers are eyeing the city.

Mayor Domenic Sarno, who plans to meet privately with potential developers next week, could play kingmaker, as the new law requires that a host community agreement be reached with city officials before an application for a casino license will be considered by the state gaming panel. Sarno did not attend Wednesday’s announcement by MGM.

‘‘We want to be here,’’ said Murren, who spoke to elected officials, business and labor leaders, and reporters. ‘‘MGM wants to be in Springfield. We think we can contribute to the economic revitalization of this city.’’

The state’s third-largest city is the birthplace of basketball and the home of the Basketball Hall of Fame, but it has struggled economically as its manufacturing base withered in recent decades. The 2011 tornado caused extensive damage to downtown businesses while damaging or destroying hundreds of homes in the area.

Gov. Deval Patrick said Wednesday he was not surprised by the level of casino interest in western Massachusetts, which also includes a proposal by Mohegan Sun to develop a resort in the town of Palmer.

‘‘It’s a large market, it’s got access to markets in other states that are close by,’’ Patrick told reporters at the Statehouse.

By contrast, only Suffolk Downs in East Boston has formally proposed a casino for the eastern Massachusetts region.

MGM said it had ‘‘under control’’ several parcels of land on which it planned to build the hotel and casio, but it would not specify whether that land would be purchased or leased. Murren added that MGM planned to bid on two separate parcels of city-owned land that would be the site of a retail complex, though the company could pursue the casino project even if it failed to secure the other parcels.

MGM said it would provide 2,000 construction jobs as well as thousands of permanent jobs and millions of dollars in tax revenue for the city.

The company has already submitted a $400,000 non-refundable application fee to the state as an initial step in the application process.

Paula Meara, a former city police chief who leads the city council’s casino site committee, said she had mixed feelings about the proposal and remained undecided about whether it would be beneficial for Springfield to host a resort casino. But she credited MGM with ‘‘doing a good job of thinking out how to build in this community.’’

Meara also praised MGM for its promise to preserve key elements of the city’s architectural history in developing the complex.