SYDNEY, Australia - If stories making the rounds are true, the Mars adventure "Red Planet" being filmed in Australia might just as well be dubbed "Prima Donnas in Space."

According to national daily newspaper The Australian, co-stars Val Kilmer and Tom Sizemore are at loggerheads, refusing to appear in scenes together and taking out restraining orders against each other.

The stories of discord became so juicy that Kilmer, Sizemore and the film's Australian producer Andrew Mason went public this week to deny them.

"Reports that Tom and I have taken out restraining orders against each other are of course completely untrue," Kilmer said in a statement. "I have known and worked with Tom for many years and have the utmost respect for him as a person and as an actor."

"Val is a good friend of mine," he said. "We've worked together on several pictures over the years and I always enjoy working with him. We shot a major scene together yesterday."

The two actors previously worked together in "True Romance" (1993) and "Heat" (1995).

The $80 million movie is now in the final weeks of shooting in and around Sydney, and at the city's Fox Studios. This follows two weeks of location shooting earlier this year in Wadi Rum, Jordan and a similar amount of time filming in the barren desert around the opal mining town of Coober Pedy, South Australia.

According to The Australian, the bad blood between the two actors emerged during filming in Jordan, when Sizemore demanded a special type of exercise machine be installed in his hotel room. In addition, the newspaper noted, the massive device had to be airfreighted from Los Angeles and then lifted to his room with a crane.

The newspaper said Sizemore's demands incensed Kilmer, and relations deteriorated so much that Warner Brothers had to dispatch veteran producer Peter McGregor-Scott to try to make peace on the set. The studio also sent a letter reminding Kilmer of his contractual obligations, the newspaper said.

Creative tensions also cited
According to The Australian, Kilmer has made clear he's not keen on either the script or first-time feature film director Anthony Hoffman, best known to date for commercials.

Kilmer is famous for his portrayals of savvy spy Simon Templar in "The Saint" and legendary rock singer Jim Morrison in "The Doors." Sizemore is most familiar from his role in Steven Spielberg's film "Saving Private Ryan."

In "Red Planet," both Kilmer and Sizemore play astronauts sent to the Red Planet in the year 2050 as part of a team of advance colonists desperate to establish a haven as humanity reaches crisis point on Earth. The film also stars Carrie-Anne Moss, who appeared in "The Matrix," and Terence Stamp, who appeared in "Star Wars: The Phantom Menace."

Situation nominal?
It's unclear whether the stories of discord on the set -- true or not -- will hurt the bankability of the movie. But film executives are taking no chances.

Adding his voice to damage control efforts this week has been the film's Australian producer, Andrew Mason. He's praised both Kilmer and Sizemore as "professional" and "hard working" actors.

"They have shown enormous patience with the rigors demanded by both our location and the substantial visual effects work and have at no time interfered in any way with the production," he said.

He praised Kilmer "calm and steady influence."

Fiona Searson, the film's beleaguered publicist, was equally categorical.

"There is no tension on the set," she said.