An independent watchdog group says that Republican John McCain's campaign violated a pledge not to air any negative TV ads on the anniversary of the Sept. 11 terrorist attacks.

The group Factcheck.org said Friday that is found a negative ad from the McCain campaign airing on Denver television on Thursday. That was the day both the Democratic and Republican camps had promised to take a break from traditional campaigning.

McCain campaign officials did not respond to repeated requests by The Associated Press for comment.

The 30-second ad criticizes the campaign of Democrat Barack Obama for what the Republicans call "disrespectful" treatment of McCain's running mate, Alaska Gov. Sarah Palin.