Mayor Richard Daley is proposing that all non-safety related services shut down for three days this year and three days next year.
The shutdown is expected to save the city close to $20 million.
Tuesday's announcement comes weeks after Mayor Daley asked the unions to agree to unpaid furlough days during the next four years. The unions refused. Mayor Daley says closing city government for six days is a hard step to take.
The mayor wants the city to close on the day after Thanksgiving, Christmas Eve and on New Year's Eve.
"All city employees will be off work, unpaid on those days except for fire and police, 911 employees, a small number of others who are normally at work on these holidays," Daley said.
If Chicago is hit by a snowstorm or other city emergency, the mayor says employees will be asked to work.
"We think that this is a poor way to run city government, government by headlines. It's not government by finding real solutions to serious problems," said Roberta Lynch, American Federation of State, County and Municipal Employees Local 31.
AFSCME represents about 5,000 city workers, and its leaders say trimming the fat on the top is a better solution.
"It's a lot of over-management in the city government. There are many situations where you have two supervisors for five workers. And those supervisors do not have enough work to do. It's just that simple," Lynch said.
With the city facing one of its worst budget shortfalls in years, the mayor says cutting and bringing in additional revenue is needed. Daley also proposed raising the parking tax from 27 to 33 percent. On Tuesday morning, parking garages passed out fliers urging customers to call their aldermen to vote against it.
"We can be very sympathetic to the fact that the budget is facing some tough times. But the wrong way to do it is to think you're going to raise revenue is by hitting the hard-working people who don't have a choice," said Cmsr. Monica Metzler, Parking Industry Labor Mgmt.
"This is going get to tougher; it's not going to get easier," Daley said.
On Wednesday, the mayor will present his budget, which will include layoffs. When asked several times about reducing city services, the mayor did not get into specifics. He only answered by saying the economy is getting worse everyday.
As for the government shutdown, union leaders questioned whether it is legal to enforce it without renegotiating union contracts.
Whether it's Streets and Sanitation or police and fire, 38,000 workers on the payroll make up more than three-quarters of the city's budget. So, any cuts to that budget will inevitably affect those workers.
But budget experts say the city has hit the perfect budget storm with low reserves, high personnel costs and a worldwide financial crisis.
"It is in a desperate financial situation in that expenses exceed available revenues," said Laurence Msall, The Civic Federation.
Mayor Daley's also plan centers on personnel, leaving vacant positions unfilled. The mayor is also expected to announce hundreds of layoffs as part of his budget presentation to the city council Wednesday.
"At the end of the day, the city of Chicago and the people that pay taxes here, their services are going to be diminished like never before," said Dennis Gannon, Chicago Federation of Labor.
The mayor plans to raise funds and cut costs with a number of other proposals, including auctioning more taxi medallions, offering sponsorships of city activities and assets and eliminating outside property management.
A year ago, facing another tough budget, the mayor raised taxes on everything from cell phones to bottled water. This year however parking is just about the only tax increase.
"The city has forced furlough days on workers in the past. But in the past those were only non-union workers, including aldermen and the mayor," Msall said.