MGM Resorts International is the latest heavy hitter to join the casino sweepstakes in western Massachusetts, a region the Mohegan Tribe staked out years ago.

The Las Vegas-based giant will be named today as the development partner for a resort casino project proposed for the tiny town of Brimfield, sources confirmed.

David Callahan, the Palmer, Mass., businessman who controls the land where the Brimfield casino would be built, announced through an email sent by spokesmen Wednesday that he will identify his choice of a partner at an 11 a.m. press conference.

Callahan, chief executive officer of Palmer Paving Corp. and a principal of Rolling Hills Estates Realty Trust, first unveiled his plans for a casino in October, telling Brimfield selectmen he was interested in developing about 150 acres his realty trust owns north of the Massachusetts Turnpike.

The property is not far from the Palmer site where the Mohegan Tribal Gaming Authority has proposed developing a resort casino off Exit 8 of the turnpike.

Under a new state law, one casino license will be awarded in each of three regions in the state - western Massachusetts, the Boston area and southeastern Massachusetts. In addition to the Mohegans, several other major gaming operators had previously announced their involvement in western Massachusetts proposals.

Hard Rock International, which is owned by the Seminole Tribe of Florida, has allied itself with a partnership that controls a Holyoke site bordering Interstate 91, and both Ameristar Casinos of Las Vegas and Penn National Gaming of Wyomissing, Pa., have expressed interest in Springfield sites.

MGM Resorts International owns and operates 15 properties in Nevada, Mississippi and Michigan, and has 50 percent investments in four other properties in Nevada, Illinois and Macau. The company, formerly known as MGM Mirage, has a partnership deal with the Mashantucket Pequot Tribe, which branded its second casino in Ledyard as MGM Grand at Foxwoods.

Amid speculation that MGM Resorts would be identified as the Brimfield partner, Mitchell Etess, chief executive officer of the Mohegan authority, said Wednesday he always expected there would be a lot of competition for the western Massachusetts license.

"No matter who enters the race, it's our position that our proposal is the best," he said. "Our location is the best and as the premier gaming brand in the Northeast we're the best choice for the Commonwealth. Nothing's going to change that."