TRENTON - A Senate leader yesterday said highway tolls should increase only to pay for transportation improvements, casting further doubt on Gov. Corzine's plan to boost tolls to reduce state debt.

Senate Majority Leader Stephen Sweeney said Corzine must find an alternative to toll hikes to pay at least half of $32 billion in state debt.

"As far as cutting state debt, he's going to have to work with something else besides this to do it," said Sweeney (D., Gloucester).

The lawmaker said the gas tax shouldn't increase, as some lawmakers suggest, since the state transportation fund has money until 2011.

"I don't see it right now," Sweeney said. "Down the road, maybe."

He said the $2.5 billion in proposed budget cuts set to be unveiled next week by Corzine - along with future limits on state spending and borrowing and renewed efforts to approve public worker health-and-retirement-benefit reforms - would instead tackle state fiscal woes.

"The way to fix it is to cut spending, shrink the government and go forward," Sweeney said.

Corzine wants to increase tolls 50 percent in 2010, 2014, 2018 and 2022. The increases would include inflation adjustments, and after 2022, tolls would increase every four years until 2085 to reflect inflation.

The money would pay debt and finance transportation, but no legislator has endorsed the Democratic governor's plan.

Sweeney said tolls should increase only to improve toll roads, including the New Jersey Turnpike and Garden State Parkway. Corzine's administration has said a 45 percent toll increase is needed to widen the toll roads and fix bridges on them.

"If you're driving the turnpike or the parkway, and I'm improving my commute, and I've raised tolls to do that," Sweeney said, "people understand that."

His comments come after Assemblyman John Wisniewski said he wanted to increase the state's gas tax 18 cents and combine it with toll hikes to fund transportation, but Sweeney said lawmakers would not approve increasing the 14.5-cent-per-gallon gas tax.

As part of his plan to revamp troubled state finances, Corzine wants to freeze state spending in the budget he's to introduce Tuesday. The plan would be for the fiscal year starting July 1.

Corzine said the spending freeze would mean about $2.5 billion in budget reductions, with cuts necessary to offset rising costs.

"The governor is pleased that an active dialogue has emerged on how to put New Jersey on the path to fiscal responsibility, while also recognizing the need to fund critical, long-term infrastructure improvements," Corzine spokeswoman Lilo Stainton said.

Possible moves include offering early retirement for state workers; eliminating the Department of Personnel as well as property-tax rebates for households that earn more than $150,000; reducing hours at parks and at motor vehicle agencies; and financing cuts for hospitals, municipalities and state colleges.