But while the former mayor said it was "natural" that tributes to that day "might not be as long or it might not be as intense," he believed there must "be a remembrance of what happened on this day forever."
Giuliani was also asked about the ongoing teachers' strike in Chicago, which has seen Republicans wary of public-sector unions siding with an unlikely ally: former White House Chief of Staff and current Chicago Mayor Rahm Emanuel.
Like GOP nominee Mitt Romney and running mate Rep. Paul Ryan (Wis.), Giuliani offered support for Emanuel as the strike entered its second day.
"It seems to me he's bargaining for exactly the right things. He's asking to be able to evaluate, if there's a difference between good teachers and bad teachers. That seems almost common sense in 21st century America," Giuliani said.
The former New York City mayor added of Emanuel, "I hope he wins."