LOS ANGELES Actor Bruce Willis sued Malaysia's Petra Group and its chairman, Tunku Imran Ibni Tuanku Ja'afar, alleging that US$900,000 of the US$2 million he invested in a ``green rubber'' venture wasn't returned to him.

A Bloomberg report said that Petra's chief executive officer, Datuk Vinod B. Sekhar, and Tunku Imram had allegedly induced Willis in 2007 to invest in a company that was developing a non-toxic and recyclable rubber, the actor said in a complaint filed on Thursday in federal court in Los Angeles.

Willis, the star of the 1988 action-film "Die-Hard,'' accuses Petra and the executives of breach of contract and unjust enrichment.

Willis was told that former US Vice President Al Gore and actor Mel Gibson also had invested in the company, Elastomer Technologies Ltd., according to the complaint. Willis had a put option, whereby for a specified period time he could get a full refund of his investment, according to the complaint.

He exercised the option on March 17, Willis said.

"Despite defendants' obligation to immediately refund Willis' investment, in April 2008, defendants continued to provide different specious excuses for the retaining of Willis' funds,'' the actor said in the complaint.

Andrew Murray-Watson, a spokesman for Kuala Lumpur-based Petra, said Willis is due to be repaid the remaining $900,000 in the next couple of weeks.

"We're very surprised Mr. Willis is taking this action,'' Murray-Watson said in a phone interview.

Willis's lawyer, Martin Singer, didn't immediately return a call seeking comment.

The case is Bruce Willis v. Elastomer Technologies, 08-7670, U.S. District Court, Central District of California.