Mayor Nutter confirmed Thursday that parts of Philadelphia will be fenced in for security during the visit by Pope Francis in September, but dismissed speculation that the whole of Center City will be behind chain links.

"Whoever is saying that somehow all of Center City is going to be shut down has no idea what they're talking about," Nutter said at a news briefing at City Hall following a trip to Mexico.

"There's never been any discussion with me where the idea of all of Center City being enclosed, encapsulated, shut down, has ever been discussed," he said.

The pope will arrive on the morning of Sept. 26 for a whirlwind of appearances, including Mass at the Cathedral Basilica of SS. Peter and Paul, a speech at Independence Hall, and the gala Festival of Families that night on the Benjamin Franklin Parkway, where as many as 1.5 million people are expected.

On Sunday, the pope will visit Curran-Fromhold Correctional Facility before celebrating Mass that afternoon, again on the Parkway with a crowd of a similar size.

Some fencing - height and type to be determined - will go up in parts of the city where the pope is expected to appear, Nutter said. The security measure is typical in other cities for large events involving world leaders, to restrict access through metal detectors.

He said it would not be the first time Philadelphia has seen such fences. "There was fencing out at the July Fourth show just the other day. . . . Fencing is not a new concept in this city."

As the city, along with the Secret Service, works to finalize the footprint of the secure perimeter and the street closures around it, Nutter encouraged Philadelphians to avoid running for the hills.

"The overwhelming majority of the city will be fairly unaffected by what's going on in Center City. Again, there will be road closures, places that you can't go, and you'll know all that over the course of the next couple months," he said.

Preliminary traffic closures involve streets from the Delaware River to the Schuylkill, as far north as Girard Avenue and as far south as South Street, sources have said.

The World Meeting of Families - the Vatican-sponsored conference that is the impetus for Francis' visit - will run from Sept. 21 to 24, ahead of the pope's arrival. Organizers are trying to secure housing for the thousands expected to attend the congress and the hundreds of thousands who will come for the pope's appearances.

The city is considering allowing camping in some areas - but not on the Parkway, the director of emergency management, Samantha Phillips, has said.

"We are looking at camping for some other areas of the city, and how we manage that, just because of the reality of the event," she said. "At the city level, we have these policies and rules and regulations, but our desire to be flexible with those and adapt to what we think we might see during the papal visit has been pretty great."

Despite the headaches that lie ahead, Nutter said, the visit is a unique opportunity worth sticking around for.

"We'll continue to pump out information and folks will make whatever decision they need to make. I would expect the majority of Philadelphians will be here and experience everything that goes on with it," he said. "I encourage patience. Have a plan, work with us. He'll be here for about 48 hours. I think most of us can get through pretty much anything in a 48-hour period."