Mayor Rahm Emanuel is trying to get more information on the environmental and economic impacts of the proposal before deciding whether to support it, mayoral spokesman Tom Alexander said.
"The mayor will work with members of City Council to reach a consensus on this issue," Alexander told the Chicago Tribune.
Alderman George Cardenas, the council's Heath Committee chairman, has suggested phasing out plastic bags over 12 to 18 months and requiring stores to sell reusable bags and offer paper bags.
Tanya Triche, a lawyer for the Illinois Retail Merchants Association, said the move would amount to a tax on grocers who have to pay for the paper bags.
Retailers argue a ban would force them into charging shoppers up to 10 cents for each paper bag, the Tribune said.
On Tuesday, the Los Angeles City Council passed a resolution banning plastic grocery bags in supermarkets and convenience stores.