U.S. Sen. Richard Blumenthal called Monday for the U.S. Department of the Interior to act "clearly and authoritatively" on the Mashantucket Pequot and Mohegan tribes' amended gaming agreements with the state, which incorporate the third Connecticut casino they've been authorized to build in East Windsor.

In letters the tribes released earlier in the day, an Interior official equivocates, saying department action "is premature and likely unnecessary."

"It's incomprehensible to me that they failed to address this issue right now because the Interior Department has the responsibility to review the agreements," Blumenthal, a Connecticut Democrat, said by phone. "The letter they sent is ambiguous and seems to delay a situation that should be addressed now rather than later."

The letters came to light hours after MGM Resorts International, the Las Vegas-based gaming operator intent on derailing the tribes' third-casino plan, unveiled an unlikely bid to develop a $600 million Bridgeport casino. Such a project would require legislative approval and would jeopardize the state's gaming agreements with the Mashantuckets and the Mohegans, respective owners of Foxwoods Resort Casino and Mohegan Sun.

The letters nevertheless could be seen as clearing the way for the tribes to proceed with their East Windsor project, which is aimed at defusing the competitive impact of MGM Springfield, the nearly $1 billion resort casino MGM expects to open a year from now in Massachusetts.

"We return the Amendment to you to maintain the status quo as action on the Amendment is premature and likely unnecessary," Michael Black, acting assistant secretary of Indian affairs, writes in identical letters addressed to Kevin Brown, the Mohegan chairman, and Rodney Butler, the Mashantucket chairman.

The letters are stamped with Friday's date.

"The Amendment addresses the exclusivity provisions of the Gaming Compact," Black writes. "We find that there is insufficient information upon which to make a decision as to whether a new casino operated by (the tribes) would or would not violate the exclusivity clauses of the Gaming Compact. The Tribes have entered an agreement with the State whereby they have agreed that the exclusivity provisions will not be breached by this arrangement. Therefore, our action is unnecessary at this time."

The letters were copied to two Nevada lawmakers — U.S. Sen. Dean Heller and U.S. Rep. Mark Amodei, both Republicans. No Connecticut legislators were copied.

Blumenthal said the "Connecticut delegation" — himself, his Senate colleague Chris Murphy and U.S. Rep. Joe Courtney, D-2nd District — have sought to communicate with the Interior Department but so far had been unsuccessful.

In a statement, a spokesman for the tribes said the letters affirm the tribes' exclusive right to operate gaming in the state.

"... It's up to (the) state and the tribes to agree that the exclusivity provisions will not be breached by their arrangement to jointly own and operate the East Windsor facility," Andrew Doba said. "We view last year's massive, bipartisan vote in favor of the project as positive proof that our state's leaders understand exactly what's at stake. We intend to work with the Governor, Attorney General and the Legislature on the next steps in moving this project forward."

MGM and a partner, The RCI Group, said they have a formal agreement to build MGM Bridgeport at Steelpointe Harbor in Bridgeport. Jim Murren, MGM's chairman and a Bridgeport native, said the proposed casino can be "a major economic force, a top-tier entertainment resort, and an essential contributor to this community," adding that "this project can help to turn the economic tide of this state. We just need the political commitment to make it happen."

Doba called the Bridgeport proposal "MGM's latest stunt."

"The idea that MGM is having a 'groundbreaking' for a project that hasn't come close to receiving legislative approval continues a pattern of dishonesty that we saw time and again during the legislative session," he said. "Simply put, authorization of this facility would violate the existing compacts between the two tribes and the state which would immediately end the slot payments that currently sends the state hundreds of millions a year in much needed revenue.

"Our state's elected officials saw through their dishonesty last session, and we expect them to see this latest fib for exactly what it is — another bought and paid for piece of misinformation."

The Mashantuckets and the Mohegans pay 25 percent of their slot-machine winnings to the state in accordance with agreements that have been in place for more than 20 years. In the fiscal year that ended June 30, the payments totaled $269.9 million.

The amended agreements signed by Gov. Dannel P. Malloy and approved by both chambers of the state legislature call for the tribes to keep making the payments and, additionally, to pay the state 25 percent of all gaming revenues — from slots and table games — generated by the East Windsor casino.

Asked for comment on MGM's Bridgeport announcement, Chris Collibee, Malloy's press secretary, said the governor's office would review it once it receives it.

"However, it is important to note that gaming is not currently authorized in Bridgeport under current law," Collibee said.

MGM officials said the company's proposed Bridgeport casino "would be New York-facing, providing access to the New York City market of 8.5 million people, as well as Fairfield and Westchester (N.Y.) counties."

The casino would include 2,000 slot machines, 160 table games, a 700-seat theater, a 300-room hotel, retail and dining options.

b.hallenbeck@theday.com