Mayor Martin J. Walsh has scored a lucrative deal with Mohegan Sun that dramatically tips the scales in favor of the Connecticut casino company in its battle for the sole Boston-area gaming license even as it puts the city on a path to arbitration with Wynn Resorts’ rival Everett bid.

Sources inside the Walsh administration familiar with the discussions said the terms will be “on par” with the estimated $52 million deal — save for revenues from real estate taxes — that Mayor Thomas M. Menino reached with Suffolk Downs last year when the track was planning a Caesars casino on its East Boston side. Eastie voters rejected the agreement in a November referendum.

“It will ensure the greatest mitigation that’s possible for the city,” a City Hall source said of the Mohegan deal, which had yet to be finalized last night. “This was really the only course of action that we felt … would protect the people of Boston.”

Mohegan Sun, whose CEO is Mitchell Etess, declined to comment.

Boston is poised to enter arbitration with Las Vegas mogul Steve Wynn, with best and final offers due Thursday. A city source characterized Wynn’s offer to Boston as “far less neighborly” than Mohegan’s. Wynn spokesman Michael Weaver said “the total package offered to Boston is millions of dollars per year.”

Clyde Barrow, a gaming expert at the University of Massachusetts Dartmouth, said the state Gaming Commission is likely to view a deal cut at the table more favorably than one reached through arbitration.

“If they reached a deal with Mohegan but not with Everett, and it’s still in that situation when it comes time to issue a license, then obviously that would tilt it in favor of Mohegan to a significant degree,” Barrow said. “The commission does look at that, and it’s part of the consideration, the generosity of the agreement.”

The gaming panel last week turned down Walsh’s request to halt its licensing proceedings until after a November vote to overturn the 2011 law that legalized casino gambling. The commission expects to award the Boston-area casino license by early September.

The defunct “host community” agreement Menino reached with Suffolk Downs called for a $33.4 million one-time, upfront community fee to pay for several projects in East Boston, including construction of a youth and senior citizen center. It also provided for $20 million annually in a community trust to offset costs from increased traffic and crime, among other expected problems.

The prior deal also called for a minimum $45 million for traffic and infrastructure improvements, including a Route 1A flyover road. The source said the traffic mitigation terms with Mohegan Sun are expected to be equal to, and possibly exceed, the Menino deal.

Under that agreement, Boston was expected to get a yearly $52 million based on projected gaming revenue generated by a Caesars casino. Regardless of revenue, the deal called for Boston never to receive less than $32 million in a given year.

In light of its Mohegan deal, the city will drop its threat to file a lawsuit arguing for “host community status” to both casinos, the subject of months of wrangling with the commission.

East Boston residents and officials cried foul when the Suffolk Downs casino was simply moved over to the Revere line after the November vote, a shift Mohegan insisted made Boston a surrounding community — a less powerful designation that denies Hub residents voting rights over the project.