Pop diva Madonna has upset US presidential hopeful John McCain by comparing the Republican with Adolf Hitler.

During a concert in Cardiff, Madonna flashed images of Adolf Hitler and Zimbabwean President Robert Mugabe followed by McCain.

In contrast Democrat candidate Barack Obama was in a sequence with John Lennon, Al Gore and Mahatma Gandhi.

McCain's campaign hit back at the comparison and angrily condemned the segment.

Madonna's swipe at McCain came during a performance of the song "Get Stupid", when the Republican contender's image was flashed up alongside images of destruction and global warming.

McCain campaign spokesman Tucker Bounds said it divisive.

"The comparisons are outrageous, unacceptable and crudely divisive all at the same time," Bounds said.

"It clearly shows that when it comes to supporting Barack Obama, his fellow worldwide celebrities refuse to consider any smear or attack off limits."