Obama said McCain has tried to tone down some of the attendees at his rallies, The Hill reported Saturday.

"I appreciated his reminder that we can disagree while still being respectful of each other," Obama said of McCain.

Some of the rallies hosted by McCain and his running mate, Sarah Palin, have sought to highlight past associations of Obama's, including his relationship with former Weather Underground leader William Ayers.

In a speech in Philadelphia Saturday, Obama said he intends to "change the world."

Appearing at the first of multiple scheduled appearances in the Pennsylvania city, the Illinois senator spoke about the troubled economy and his mission of bringing about a better Philadelphia and overall nation, Philadelphia's KYM-TV reported.

"We have a history of overcoming, Philadelphia. That's what America is about. That is what we are fighting for," Obama said at the Progress Plaza event. "I promise you we won't just win Philadelphia. We will win Pennsylvania and you and I together are going to change this country and we are going to change the world."

Philadelphia Mayor Michael Nutter said prior to Obama's first appearance that his city was ready to put forward its best face during the campaign stop, the Philadelphia Daily News reported.

"What we've communicated to the campaign is, look we know how to do elections," said Nutter. "If you give us the candidate and give us a decent amount of time, we'll put on something you've never seen in the United States of America."