Nicole Kidman was enthusiastic about the trilogy at Cannes

The Oscar-winning actress is busy on other films until October and von Trier feels he cannot wait, reports industry website Screen Daily.

He has decided to crack on with his project using different actresses in the lead role of Grace.

Kidman's split from the project comes despite assurances made at Dogville's Cannes festival debut that she was secured for the trilogy.

Von Trier's producer Vibeke Windeloev said the loss of Kidman could not be helped.

"She really wanted to do it, and we really wanted her... for both financial reasons and because of Lars' many other projects, we just have to stick to our March-April start date," Windeloev told the website.

"The Americans might be used to film schedules being set after the availability of the stars, but we just couldn't postpone the shoot until it fitted Nicole's," she added.

The film will be entitled Manderlay and all the parts are yet to be cast.

'Controversial'

Von Trier's US triology deals with the issue of slavery in America's deep south.

The first instalment, Dogville, begins in the 1930s. Paul Bettany stars alongside Kidman.

Dogville premi�red amid much excitement at 2003's Cannes festival.

It was seen as the favourite to win the festival's prestigious Palme d'Or but it came away empty-handed. The award went to Gus Van Sant's Elephant.

At the time, the head of Von Trier's Zentropa production company, Peter Aalbeck Jensen, said the jury's decision was "politically correct" and Dogville had been "too controversial".

Vibeke Windelov accused the jury of making a political choice because Dogville was seen as anti-American.

Von Trier won the Palme d'Or in 2000 for Dancer in the Dark, the third film in his Danish trilogy.