MGM Resorts will begin construction of a seven-level, 3,400-space parking garage this month, a significant step forward for the company’s plans for a casino and hotel complex in downtown Springfield.

MGM announced Thursday that it had awarded a contract for the project to a partnership of Tishman Construction, an international firm, and Fontaine Bros. Inc., which is based in Springfield.

MGM said the parking garage should be finished by the end of 2017, with the casino to open about a year later. “We are excited to see construction on the garage move forward,’’said Michael Mathis, MGM’s top executive in Springfield.

The casino, which will cost an estimated $950 million, is the largest construction project under development in Western Massachusetts.

MGM, an international resort and casino company based in Las Vegas, announced the contract while presenting its quarterly report to the state Gaming Commission at its meeting in Springfield.

The commission also voted to accept changes to the casino’s design, including the removal of a hotel tower in favor of a low-rise building and a reduced overall footprint. MGM has said the redesign saves money and better integrates the project into the downtown.

The casino complex is expected to include 75 table games, 3,000 slot machines, and a 250-room hotel.

Sean P. Murphy can be reached at smurphy@globe.com. Follow him on Twitter @spmurphyboston.