TRENTON - Without a resolution to a transportation funding stalemate, Senate President Stephen Sweeney said Thursday that he remained opposed to calling a vote on a proposed constitutional amendment that would require the state to make bigger payments into its pension system.

Sweeney (D., Gloucester) did not explicitly rule out posting the amendment Monday - the deadline for a vote on the measure, which public-sector unions are calling for, to get on the November ballot.

But Sweeney said he would not support the amendment before reaching a deal to replenish the depleted Transportation Trust Fund.

Sweeney and Assembly Speaker Vincent Prieto (D., Hudson) previously agreed on a bill to more than double the state's gasoline tax, to 37.5 cents per gallon, while also cutting taxes on estates and retirement income for seniors.

Sweeney said Thursday that he did not have enough votes to override an anticipated veto by Gov. Christie, who has advocated for a sales tax cut to offset the gas tax hike. Sweeney contends that cut would put too large a hole in the budget.

Until the transportation funding impasse - which spurred Christie to shut down road projects - is resolved, "we can't in good conscience put a constitutionally guaranteed pension payment on the ballot," Sweeney said at a Statehouse news conference. "It would fail."

Of whether he could garner the 27 votes he needs for the transportation bill in time to post the pension amendment Monday, Sweeney said, "I've been holding out hope each day, but we're almost out of time now."

Even without the amendment, the state is ramping up its payments into the pension system, Sweeney said. He said there would be no harm in waiting a year on the amendment, which was intended to help stabilize the long-underfunded system.

"I think I've proven myself over the years," Sweeney said of his commitment to public workers. "I care about pensions."

Sweeney drew backlash from leaders of unions including the New Jersey Education Association - which Sweeney had accused a day earlier of trying to bribe lawmakers to force a vote on the pension question.

Sweeney "has betrayed every New Jersey public employee," Wendell Steinhauer, the president of the teachers' union, said in a statement Thursday. "His excuses, rationalizations, and shifting positions don't change the fundamental fact that he lied." Steinhauer said Sweeney had promised to put the question on the ballot.

Hetty Rosenstein, state director of the Communications Workers of America, said Sweeney was wrong to link the pension amendment to the transportation funding situation.

"The fact that Senate President Sweeney - at the eleventh hour - will not post it for a vote is the exact reason we're demanding a constitutional amendment," she said in a statement.

Sweeney, who sponsored the proposed amendment, said the state could afford both the amendment and the transportation "bill we have right now," which he said would phase in tax cuts over four years.

What would be unaffordable, Sweeney said, is the proposal Christie supports - which Prieto had agreed to - that would cut the sales tax one percentage point in exchange for the 23-cent-per-gallon gas tax increase. New Jersey's 14.5-cent-per-gallon tax on gasoline is the second-lowest in the country.

Without knowing how much a final transportation agreement will cost, Sweeney said, it would be irresponsible for him to move forward with the pension amendment.

"Say we compromise," and the transportation plan ends up costing more, Sweeney said. "So I've got to face reality."

Construction groups joining Sweeney at the news conference said they needed the state to solve the funding issue.

Since Christie ordered the road-project shutdown last month, "we have hundreds of firms that are affected. We have thousands of employees that are laid off," said Robert Briant, CEO of the Utility and Transportation Contractors Association of New Jersey.

With workers needing to make money now to carry them through winter, "we need this resolution. We needed it yesterday," he said.