Boston (AP)  -- As Senate leaders unveiled a $28 billion budget Wednesday that relies heavily on new taxes and savings, Republicans pledged to file Gov. Deval Patrick's casino bill as an amendment to the spending plan, saying the state needs new sources of revenues.

The move, which could breathe new life into Patrick's plan, comes a week after the governor told a Brookline Chamber of Commerce audience that his legislation to legalize casino gambling in Massachusetts "may yet come back."

The House earlier this year overwhelmingly defeated the casino measure, essentially killing it for the year, but Republicans say they want to give the Senate, which has supported expanded gaming in the past, a chance to vote on the plan.

"We want to fortify the governor's efforts going forward if he intends to refile the bill in the new year," said Republican Sen. Michael Knapik, R-Westfield. "Plus, we need the money."

The Senate budget raids the state's rainy day fund for nearly $400 million and relies on hundreds of millions of dollars in new revenues from a proposed $1-a-pack cigarette tax hike and the closing of so-called business tax loopholes.

Senate Ways and Means Chairman Steven Panagiotakos, D-Lowell, said the budget plan was fiscally responsible.

"These recommendations are a balanced, fair approach to addressing the most pressing needs of the commonwealth while remaining mindful of the declining economy," Panagiotakos said.

Besides the $400 million from the state's rainy day fund, the budget also relies on $175 million in projected revenues from the cigarette tax, $297 in added revenues from the business loophole closings and another $157 million from tighter enforcement by the Department of Revenue.

He also said the budget includes "tens of millions" in cuts.

One of the biggest question marks in the budget is funding for the state's 2006 landmark health care law. Senate budget writers used an estimate of $869 million to cover the law's subsidized health care program known as Commonwealth Care.

But the administration's own, more current estimates -- based on the unexpected success of the program -- have added about $200 million to the cost. That's in addition to the $200 million above original estimates for MassHealth, the state's Medicaid program.

Critics say the $400 million in higher-than-expected health care costs on top of the $400 million the plan already draws from the rainy day fund and other, smaller cost increases could force the state to draw as much as $1 billion from the rainy day fund.

"If you look at the structural balance, meaning revenues coming in and spending going out, it's about a billion dollar gap," said Michael Widmer, president of the business-backed Massachusetts Taxpayers Foundation.

Panagiotakos defended using the original Commonwealth Care estimate, pointing out the same estimate was used by the House when it drafted its budget. But he also expressed concern about drawing too much from the rainy day fund, meant to help the state weather fiscal slumps.

"We are going to need that rainy day account if we get into any type of major economic downfall," he said.

Panagiotakos, who also supports casino gambling, said there's nothing stopping Republicans from offering Patrick's bill as an amendment.

He wouldn't say whether he thought the amendment would pass.

"There are going to be a lot of amendments and we are going to take them up one by one," he said.

Asked last week during a Brookline Chamber of Commerce address about whether his casino plan was dead or not, Patrick said: "It may yet come back in the Legislature. I acknowledge it's hard."

Besides pushing the casino amendment, Knapik also said he was concerned with the spiraling cost of the health care law, saying it's siphoning money away from other pressing needs.

He said the Senate should consider restricting parts of the law, designed to mandate health care to virtually all Massachusetts residents.

"We ought to have that debate," he said. "We've got to put the entire discussion of the scope of the law on the table."