PROVIDENCE — Twin River’s owners say they will have to pull the plug on overnight gambling if state lawmakers — or the Carcieri administration — are unwilling to extend the trial period they were given a year ago to prove that 24-hour slot play on weekends and holidays is a money maker.

Since its approval by the General Assembly in May 2008, overnight gambling has been credited by the Lincoln venue with producing an additional $12.1 million for the state, more than half of it — $6.7 million — sprinkled about in school aid.

But the one-year trial period ends on June 30.

“As a result, we will be legally prohibited from maintaining the current hours of operations. We are therefore preparing to reduce hours and resume the 2 a.m. closing beginning July 1, 2009,” Twin River senior vice president and legal counsel Craig Eaton wrote Gary Sasse, in his capacity as director of the state Department of Revenue, in a letter on Monday.

Eaton said Twin River needs the state to act before then, and even suggested the Department of Revenue could permanently extend the hours beyond June 30 on its own, without need of legislative action.

There was no immediate response from key lawmakers to the letter, dispatched by Twin River less than a week after the owners of the financially struggling greyhound track and slot parlor served notice they intend to suspend live dogracing on Aug. 8. That cost-cutting proposal elicited immediate howls from the dog owners, and statements of “deep concern” from key lawmakers.

But there does not appear to be resistance to extending the overnight gambling authorization in the legislature or administration, which has now extended, multiple times, the opportunity lawmakers gave the slot parlor last year to offer “free-play” as a reward for frequent players. The initial three-month, $1.5-million giveaway program was extended by the administration in October, and monthly after that in amounts of up to $750,000 per month at a cost so far of $4,176,810.

In a brief interview on Monday, Sasse said 24-hour gambling on weekends and on the nights before state and federal holidays — known in State House shorthand as “24/3”— has “proven to be in the financial interest of the state ... [so] if the General Assembly does not extend the authority to continue 24/3, we are prepared to do it administratively.”

State lawmakers have their own hearing scheduled for Wednesday on a bill [S0286] sponsored by Sen. Frank Ciccone — a top official in the Laborers’ International Union in Rhode Island — to extend the deadline. Ciccone, D-Providence, said he believed legislation was, in fact, necessary and he was unaware of any opposition to it.

But that said, Eaton’s letter put the lawmakers on notice they cannot wait until the final hours of the legislative session as they often do for their major decision-making.

In his letter, Eaton said: “In order to comply with certain provisions in our collective bargaining agreements we will need to be advised by June 1, 2009 of DOR’s decision ... Unless informed otherwise, we will continue preparations for the change in hours in accordance with an anticipated sunset of the legislation.”

Spokeswoman Patti Doyle said it was not clear that a rollback in hours of operation would result in any layoffs, beyond those likely to result from the suspension of dog racing. “I suspect that won’t be definitively known until we go through the collective bargaining process,” she said. But, “it might be more a matter of lost shifts for some employees who won’t necessarily lose their job but their wages would be impacted by shift reduction in the event of a rollback to 2 a.m.” She said “30-40 employees” would likely be impacted by reduced hours.

Twin River is owned and operated by UTGR Inc., a subsidiary of BLB Investors — the holding company comprising Kerzner International Limited, Starwood Capital Group and Waterford Group LLC.

The company bought the aging Lincoln Park dog track in 2005, along with three greyhound racetracks and a horse track in Colorado, and then embarked on a $225-million renovation and expansion in Lincoln.

Twin River has been struggling to keep its lenders and other creditors at bay since March 2008, when it defaulted on more than a half-billion dollars in loans it borrowed from a consortium led by Merrill Lynch Capital Corp. to buy and renovate the former Lincoln Park.

With the state counting on $246.8 million this year alone from the 4,752 video-slots at Twin River, the state’s stake in the financial well-being of the sprawling gambling hall is huge. Out of every $1 left behind by players, 61.45 percent goes to the state and 27.8 percent to the owners, with the rest divided up among the Town of Lincoln, machine suppliers and the Narragansett Indian tribe, which has no involvement in the ownership or operation.

kgregg@projo.com