“There’s a definite hole in the budget, and neither taxpayers or employees should be expected to fill it alone,” said Kelley Quinn, a spokeswoman for the mayor. “The longer we delay, the worse the problem gets.”

Union leaders are not in such a rush.

“There certainly seems to be a will to address Chicago’s pensions, and obviously the mayor is pushing that vigorously,” said Daniel J. Montgomery, president of the Illinois Federation of Teachers. “But if they are looking to duplicate what they did to the state systems, they’ve got a few legal hurdles.”

For one thing, he said, the Illinois Constitution has “very clear and precise language” that guarantees that retirement benefits cannot be lowered. The ruling on Tuesday by the judge overseeing Detroit’s bankruptcy that federal law trumps the Michigan Constitution when it comes to lowering benefits does not apply in Illinois, Mr. Montgomery said.

“The City of Chicago is not bankrupt,” he said. “It is an entirely different situation.”

Michael K. Shields, president of Chicago’s Fraternal Order of Police, said there was no way to compare the new state bill with the situation faced by his members. “This pension bill is not one size fits all,” he said.

He pointed out that much of the benefit cuts in the state law came from changes in the way annual cost-of-living raises are dispensed. While state workers received annual raises of 3 percent that compounded every year, Chicago police officers and firefighters receive a flat raise of at most 3 percent that does not compound. So more benefit cuts would have to be found elsewhere for those city workers.

Other union leaders were even more blunt.

Karen Lewis, president of the Chicago Teachers Union, which represents 30,000 people, called the whole process an unnecessary attempt on behalf of bankers and the financial community to force government workers out of defined benefit pension plans and into 401(k) plans.

“Our actual problem with this bill is that, once again, the people who are behind this thing are the very people who stand to gain from our members going into 401(k)’s,” Ms. Lewis said. “They will get those fees from administering the 401(k)’s. These people are hypocrites, and they should be ashamed to open their mouths.”