'Iron Man' holds on to US top spot

Iron Man has held off competition from Speed Racer and What Happens In Vegas to retain the US box office top spot.

The Marvel superhero adaptation added $50 million to its US takings, bringing its running total to $177 million after two weekends on release.

Speed Racer, the first Wachowski brothers-directed film since The Matrix Revolutions, entered the chart at number two, with the Ashton Kutcher and Cameron Diaz Vegas comedy just behind at three.

The top ten's only other new entry is David Mamet's Redbelt. The mixed-martial arts film expanded its theatrical release and climbed from number 41 to number 10 in the chart.

The top ten US box office films in full:

1. (1) Iron Man - $50.5 million
2. (-) Speed Racer - $20.2 million
3. (-) What Happens in Vegas - £20 million
4. (2) Made of Honour - $7.6 million
5. (3) Baby Mama - $5.8 million
6. (5) Forgetting Sarah Marshall - $3.8 million
7. (4) Harold and Kumar Escape from Guantanamo Bay - $3.2 million
8. (6) The Forbidden Kingdom - $1.9 million
9. (7) Nim's Island - $1.3 million
10. (41) Redbelt - $1.1 million