TRENTON -- As New Jersey lawmakers prepare to converge at the Statehouse on Thursday to vote on a state budget ahead of the July 1 deadline, state Assembly Speaker Vincent Prieto told NJ Advance Media he is not budging in his opposition to a proposed compromise that would avoid a government shutdown.

"I'm cemented," Prieto said before walking into his office for a closed-door meeting with the Assembly's minority leader, Jon Bramnick (R-Union), and other legislators.

At issue is a pivotal piece of budget negotiations: A plan to allow the state to tap into the reserves of Horizon Blue Cross Blue Shield of New Jersey, something Gov. Chris Christie has demanded.

"I don't support that bill," Prieto said, reaffirming his stance for the past few weeks as negotiations have reached a boiling point.

Christie has dug in his heels as the budget debate has raged on against the midnight Friday budget deadline. If there's no budget in place, Christie has the authority to shut down state government.

The bill has support from Democrats who are eager to cash in on the perks in the budget that benefit their districts, which Christie, who's readying to sign his last budget, could strike out with the swipe of a pen.

It's possible Democrats will try to force Prieto's hand when they go behind closed doors on Thursday. One option would be to refuse to give Prieto the votes within his own party to pass the budget unless he capitulates on the Horizon fight.

The speaker said Thursday morning he's readying himself for members of his caucus to do just that, saying, "I'm going to (post) a budget and whoever doesn't vote for a budget is going to shut government down."

Shortly after going behind closed doors with Bramnick, the minority leader left Prieto's office and declined to discuss details of the brief meeting. But he hinted at a raucous day among Democrats to come.

"This is why the Republicans should be in charge of the Legislature," he quipped.

About an hour later, Prieto's office issued a statement blasting the Horizon bill.

"To be clear -- the budget bill has nothing to do with the reworking the state's largest health insurer in four days, for no apparent reason, during a time when Trumpcare threatens millions of Americans," Prieto said in the statement.

"The Horizon bill is an unfair Christie tax on the insurer's 3.8 million policyholders. I will not negotiate on that bill as part of the budget process."

Matt Arco may be reached at marco@njadvancemedia.com. Follow him on Twitter @MatthewArco or on Facebook.