Britney wants Madonna to join her on tour

Britney Spears is planning to unveil superstar pal Madonna as a surprise guest when she kicks off her comeback tour next year.

Spears joined Madonna onstage in Los Angeles last month during the US leg of her 'Sticky & Sweet' tour - and Spears wants Madonna to return the favour when she hits the road in New Orleans, Louisiana in March.

The singer's choreographer Wade Robson reveals, "I'm choreographing and set-designing her show.

"There's been talk of Madonna making an appearance, and there's so many places we could take that. At this point the main issue is timing."