The new Ben Stiller comedy, Tropic Thunder, is set to displace The Dark Knight at the top of the US box office this weekend.

The new Batman film has topped the chart for the last four weeks, breaking numerous records along the way.

Tropic Thunder, a comedy about a Vietnam film starring Stiller, Jack Black, Robert Downey Jr and Steve Coogen, was released on Wednesday.

The film grossed about $6.5 million (£3.5 million) in its first day on release and is expected to take over $40 million (£21.5 million) for its first five days.

The Dark Knight's takings, meanwhile, are predicted to fall about 40 per cent from last week, meaning it will likely sit behind Tropic Thunder and Seth Rogen-comedy Pineapple Express in this week's chart.

Tropic Thunder received its US premiere in Los Angeles on Monday night.

The event was marred by demonstrators gathering outside the cinema to protest at the film's repeated use of the word "retard".

15/08/2008 11:35:20