Elijah Wood voices the tap-dancing penguin hero of Happy Feet

Happy Feet took $42.3m (�22.3m) in its first three days of release, according to studio estimates.

Casino Royale, in contrast, made $40.6m (�21.4m) over the same period - though it did play on almost 400 fewer screens than its computer-animated rival.

Spoof documentary Borat, last week's top film, slipped down to three.

Featuring the voices of Hugh Jackman and Nicole Kidman, Happy Feet has drawn comparisons with the Oscar-winning nature documentary March of the Penguins.

NORTH AMERICAN BOX OFFICE 1. Happy Feet ($42.3m) 2. Casino Royale ($40.6m) 3. Borat ($14.3m) 4. The Santa Clause 3 ($8.2m) 5. Flushed Away ($6.8m) 6. Stranger Than Fiction ($6.6m) 7. Babel ($2.9m) 8. Saw III ($2.8m) 9. The Departed ($2.6m) 10. The Queen ($2.3m)

It is directed by Australian film-maker George Miller, producer of the Mad Max and Babe films, and features a vocal cameo from the late TV naturalist, Steve Irwin.

Casino Royale made a further $42.2m (�22.2m) outside the US and Canada, with more than half that total coming from the UK.

Its first weekend total in the US was down on the $47.1m (�24.8m) made by the previous Bond film, Die Another Day, when it opened in 2002.

However, its three-day takings were up on the Bond film before that, The World Is Not Enough, and GoldenEye, the last film to star a new actor in the 007 role.