Kidman worked with Luhrmann on the hit musical Moulin Rouge

Production on the untitled romance was due to begin shooting in the Australian outback in September, reports trade paper the Hollywood Reporter.

But Crowe will not have completed filming on Ridley Scott's American Gangster, which starts in July.

Meanwhile Kidman has begun work on a new film from director Noel Baumbach.

The film will see Kidman starring opposite King Kong's Jack Black and Jennifer Jason Leigh. Baumbach received an Oscar nomination for his work on The Squid and the Whale earlier this year.

Luhrmann's films include Romeo + Juliet and Strictly Ballroom

Crowe is rejoining Gladiator director Scott for American Gangster, which sees him playing a US detective opposite Denzel Washington's drug baron.

He recently told the Sydney Morning Herald he was still in touch with Luhrmann about his film.

"We talk, he is mysterious," Crowe told the paper. "But it's all good."

Japanese bombing

Luhrmann has said the new film, which he plans to co-write with screenwriter Stuart Beattie, will be in the mould of classic romance Gone With The Wind.

He told newspapers in Australia earlier this year the film would be set in the country during the 1930s and leading up to the Japanese bombing of Darwin.

He added the $150m (�85.6m) film would be on the scale of the David Lean's epic Lawrence of Arabia.

Crowe and Kidman were due to co-star in another film, Eucalyptus, last year, but that project collapsed due to script problems.