Mohegan Sun and the town of Palmer, Mass., plan to announce an agreement on Thursday, moving forward a process that could result in a $1 billion resort casino in the western Massachusetts town.

After the agreement is signed, the proposal will be put to voters in 60 to 90 days. Palmer residents voted support for a similar casino plan in 1997, though it did not come to fruition.

Palmer is now one of three towns competing for the sole gaming license to operate a resort style casino in western Massachusetts. The other two plans in western Massachusetts are Hard Rock Hotel & Casino in West Springfield and MGM Resorts International in Springfield.

In Palmer, Mohegan Sun is planning a casino along with a 70,000-square-foot adventure-themed water park and 300,000 square feet of entertainment, dining and retail.

The agreement between the Mohegan Tribal Gaming Authority, based in Connecticut, and the town of Palmer, Mass., will include annual "mitigation payments" to the town. Details about those payments will be disclosed Thursday at a media event and a public signing of the agreement at Palmer Town Library.

Palmer is the last of the three Western Massachusetts towns to have a host agreement, which is required for any resort-style casino. Voters will agree to, or reject, the casino plan during an election held 60 days to 90 days after the agreement is signed, as required by state gaming laws.

Springfield residents voted their support of MGM's proposal, 58 percent to 42 percent, on July 16. West Springfield residents will vote on Hard Rock's plan Sept. 10.

The Massachusetts Gaming Commission will vote early next year to decide which plan is best for Western Massachusetts. A similar process is playing out for the Boston region and the southeastern part of the state.