At a hearing on the measure Tuesday morning, House Speaker Michael Madigan called the pension shortfall — the worst of any state in the country — "one of the most serious problems affecting the state of Illinois."

"Change must be done," the Chicago Democrat said.

But public-employee labor unions called the plan unfair and unconstitutional and were continuing their efforts to kill it. Dan Montgomery, president of the Illinois Federation of Teachers, said it would severely cut the retirees' benefits and could only be described as "theft."

"How can you do this to the good people who serve our state?" Montgomery said.

Nine of the 10 members of a bipartisan pension conference committee signed off on the deal late Monday, sending it to the floors of both the House and Senate, where votes were expected later Tuesday. But passage in those Democrat-controlled chambers is not a sure bet. The committee's chairman, Sen. Kwame Raoul, said Senate President John Cullerton was still working to ensure "yes" votes Tuesday morning.

Illinois' unfunded pension liability was caused primarily by lawmakers who failed for decades to make the state's full payments to the funds.

Even as other states with similar pension messes took action in recent years, the General Assembly was unable to come up with its own solution. Meanwhile, the major credit rating agencies downgraded Illinois to the lowest credit rating of any state in the country, and annual pension payments grew to about one-fifth of the state's general funds budget, taking money away from schools, roads and other areas.

The pension proposal is estimated to save the state $160 billion over 30 years and fully fund the systems by 2044.

It would push back the retirement age for workers ages 45 and younger, on a sliding scale. The annual 3 percent cost-of-living increases for retirees would be replaced with a system that only provides the increases on a portion of benefits, based on how many years a beneficiary was in his or her job. Some workers would have the option of freezing their pension and starting a 401(k)-style defined contribution plan.

Also included in the plan is language to prevent "pension abuses," as nongovernment employees such as union bosses couldn't participate and new hires wouldn't be able to bank sick or vacation time to boost pensions.

Gov. Pat Quinn and other supporters on Monday stressed the importance of the vote, saying approving the legislation is a crucial step toward improving Illinois' disastrous financial situation. Quinn, a Chicago Democrat, planned to travel to the state Capitol and meet with as many legislators as possible to try to get them to vote yes.

"I think (this is) the most important fiscal vote that will ever be taken by the General Assembly in my lifetime," he said Monday at an unrelated event. "We need to erase the liability and move Illinois forward. That's what I'm committed to and I think everyone who is interested in the future of Illinois, the common good, what's good for taxpayers should join us in urging a yes vote."

Others have said the plan doesn't cut benefits enough, while some critics say legislators and the public haven't had sufficient time to review and analyze the legislation.

Tuesday's vote is scheduled to occur one day after the deadline for candidates to file with the state board of elections to run in the 2014 primary — timing that could give some lawmakers concerned about a primary challenge the freedom to vote in favor of the bill.

It's also a big vote politically for Quinn, who has made fixing the pension problem his top priority and is seeking another term next year. Just one of his three potential Republican challengers, Sen. Bill Brady, has said he supports the bill.