The Mashantucket Pequot and Mohegan tribes are expected Thursday to release their joint venture’s request for proposals for a third Connecticut casino.

An announcement has been scheduled for 11:30 a.m. on the steps of the State Office Building, 165 Capitol Ave., Hartford.

The request for proposals is expected to provide details of the project the tribes hope to develop in a willing “host” municipality along the Interstate 91 corridor north of Hartford.

A $200 million to $300 million casino in that area would be expected to compete with MGM Springfield, the $800 million resort casino that is being built miles from the Connecticut border.

The Massachusetts casino has the potential to divert revenue and jobs from Connecticut, which receives a 25-percent share of the slot-machine revenues generated by Foxwoods Resort Casino and Mohegan Sun.

The request for proposals is expected to be posted on the website of the state Department of Consumer Protection.