The Dixie Chicks and Toby Keith have canceled their plans to appear together in a TV ad about global warming, according to the San Jose Mercury News. Sponsored by the Alliance for Climate Protection, the campaign features public figures with opposing political viewpoints speaking out about global warming. Keith told the newspaper the Dixie Chicks were not available on the two dates that he had open, and after he agreed to a third date, the band again wasn't available. Keith said, "It's hard to get people that don't get along to agree when all those egos and stuff are involved." Noting that he's never spoken to the trio, he noted, "We've never met, officially."