The public-private partnerships could be with individuals, corporations, nonprofits or community groups, Nutter said, noting officials have received interest in five or six of the sites.
"We are working diligently every day on this issue," Nutter said.
The mayor, who estimated the library closings will save the city $8 million a year, said he expected books, computers and other materials to stay at the "knowledge centers." But he could not say if the facilities would be staffed by librarians.
Meanwhile, two floors above Nutter's news conference at City Hall, a judge heard legal arguments from people seeking to prevent the planned Thursday closings.
Library advocates have been extremely vocal since the mayor - citing plunging tax revenue as a result of the international economic meltdown - announced the budget cuts in November. Seven residents and a municipal union sued last week to stop the library closures, contending they are illegal and endanger poorer communities that don't have the luxuries of big chain bookstores and home Internet access.
"Libraries are no longer just depositories of book and magazines and other media," plaintiffs' attorney Irv Ackelsberg argued Monday in Common Pleas Court. "(They are) sanctuaries of learning and safety for our children within the streets that hold many dangers for them."
Ackelsberg cited a 1988 ordinance that states "no city-owned facility shall be closed" without the approval of City Council. He asked Judge Idee Fox to prohibit the mayor from closing the branches unless council approves.
City attorneys argued the libraries are not closing because they are slated for reuse, and that the city charter requires the mayor to balance the budget.
The reuse concept didn't sit well with Zachary Hershman, one of a few dozen protesters at the mayor's news conference.
Hershman, 23, said the closing of the library in his Kingsessing neighborhood will lead to more dropouts, unemployment and crime in an already poor and violent area. The next nearest branch is overcrowded, he said, with long waits for Internet use that many residents need to access online job applications.
"It's the only place they can go to get computers," Hershman said.
Nutter did not describe the reuse plan as privatizing or outsourcing library services, which some U.S. communities have done. Instead, the mayor said the "knowledge centers" would offer services based on each neighborhood's needs.
Still, American Library Association president Jim Rettig said libraries work best as publicly funded entities with trained staff.
"It makes as much sense to privatize your libraries as it does to privatize your police force," Rettig said. "You want people who know the community (and) its needs. This takes time over years and years to develop."
To tell people to use another branch doesn't help, he added.
"Each branch has its own character," Rettig said. "To say they can go to another branch - if that happens there will be a real adjustment period."
The mayor is making other cuts, including lowering limits on curbside trash collection, consolidating fire companies, cutting back on snow removal and cutting funding to the city's annual New Year's Day /*Mummers*/ Parade.
Nutter also planned to close three ice rinks unless private funding could be found. Officials later struck a deal with the Ed Snider Youth Hockey Foundation to operate them and two others. Snider owns the Philadelphia Flyers.
The city plans to close 68 of 81 swimming pools this summer.