Madonna has called staging her Super Bowl show "daunting." (Martin Fraser/Getty Images)

She's performing this year's Super Bowl half-time show, but Madonna confessed recently that she hasn't watched a football game from start to finish in decades.

"For sure, when I was in high school and I was a cheerleader, OK?" she told "Nightline" anchor Cynthia McFadden. "But not since then."

The pop icon said she watched a lot of soccer games during her dozen years spent living in the United Kingdom, where she enjoyed "seeing legs."

"When you play soccer, you see the legs. You see the bodies," she said. "Football, it's hard to see everybody.  They're very covered."

But uniform gripes aside, Madonna, 53, didn't downplay the importance of the game. "In the middle of this very important event in Americans lives, I have to put on the greatest show on earth," she said.

And that show, she noted, comes with serious time constraints and practical limitations. "I have eight minutes to set up my stage, 12 minutes to put on the greatest show on earth, and I have seven minutes to take it down.  So, that football field is clean for the second half of the game," she said. "How do you do that?"

The Super Bowl will take place two days after the release of Madonna's other big project, her new film "W.E." Madonna makes her feature-length directorial debut with the movie, which explores the love story between American divorcée Wallis Simpson and King Edward VIII, who abdicated his throne to marry her.

Simpson, she said, "was just a simple girl from Baltimore" without money, an education or great beauty. "One could look at the story from the outside and scratch their head and say, 'Well, when he could have anything. Why would he choose her?  And why would he give up the throne?"

Madonna said she believes the film "will find its audience."

For the Super Bowl, meanwhile, the Material Girl won't have to worry about finding an audience. There will likely be more than 100 million watching from home, not to mention the tens of thousands of football fans filling Lucas Oil Stadium in Indianapolis.

Asked what was more scary, the opening of her film or performing the live half-time show, Madonna picked the latter.

"The Super Bowl," she said, "for sure."

Watch more of Cynthia McFadden's interview with Madonna on full episodes of " 20/20" and " Nightline."