Actor Sean Penn called Wednesday on Bolivia's President Evo Morales to order the release of a US businessman who has been jailed for 18 months on money laundering charges.

The Oscar-winning actor, whose activism on behalf of humanitarian causes have made him a well known figure in Latin America, personally attended a court hearing for wheel-chair bound Jacob Ostreicher Tuesday in the eastern city of Santa Cruz.

The 55-year-old investor in a Bolivian rice growing venture was accused of money laundering when he was arrested June 2011. Ostreicher claims that authorities trumped up the charges to extort money from him.

"I ask President Morales for the immediate liberation and exoneration and safe return of Jacob to his family in the United States," Penn said at a news conference in Santa Cruz with Ostreicher.

Penn, who won Oscars for his performances in the movies "Milk" and "Mystic River," warned that the Ostreicher case could be used by "the forces of corrupt opposition to discredit president Morales."

The news conference was held at a clinic where Ostreicher is currently being held under police custody.

A district court on Tuesday referred the case to a lower-ranking judge, delaying a resolution on the request for Ostreicher's release.

Ostreicher said, "It's not that the Bolivian system of justice is bad. The problem is that is had been hijacked by a group of criminals."

The case has caused a major scandal in Bolivia as even the government has admitted the existence of a network of government lawyers and prosecutors who engaged in extorting prisoners.

About 10 people have been detained as part of an official investigation into the extortion not only of Ostreicher, but also opposition politicians and common criminals.