Mashantucket Pequot and Mohegan tribal leaders will sign an agreement Thursday formalizing the tribal partnership that will pursue a casino project between Hartford and the Massachusetts line.

State officials and representatives of organized labor are expected to attend the signing at 1:30 p.m. at the State Capitol.

The Mashantuckets and the Mohegans, owners of Foxwoods Resort Casino and Mohegan Sun, respectively, hope to develop a "satellite" casino along the Interstate 91 corridor to fend off competition from MGM Springfield, the $800 million destination resort being built near Connecticut’s border.

Tribal representatives are also expected to identify a third party that will be involved in drafting a request for project proposals. 

A state law enacted this spring authorized the tribes to plan a project and negotiate an agreement with a "host" municipality. The legislature would still have to approve the project.

MGM Resorts International, the Las Vegas-based gaming giant behind the Springfield project, has challenged the law, claiming in a federal lawsuit that it's unconstitutional because it allows only the tribes to pursue a commercial, off-reservation casino in the state.