A judge has canceled a Live Earth concert planned for Saturday in Rio because police said they did not have enough officers to guarantee crowd safety.

Organizers of the free show on Rio's Copacabana Beach said Wednesday they were trying to overturn the order to prevent Latin America from being left out of the worldwide music fest aimed at stopping global warming.

Promoted by former U.S. Vice President Al Gore, Live Earth concerts are scheduled for London; Tokyo; Johannesburg, South Africa; Shanghai; Sydney, Australia; and Hamburg, Germany; and East Rutherford, New Jersey. A band of scientists also will perform in Antarctica, to bring the festival to seven continents.

But South America may be left out after Brazilian prosecutor Denise Tarin requested a suspension of the concert, saying there were not enough officers to police a crowd that could top 700,000.

Rio police already are busy making sure Rio stays safe during the July 13-29 Pan American games, seen as a huge test for Brazil to prove it is capable of hosting major international sporting events.

Thousands of officers are cracking down on drug gangs that dominate many of Rio's slums. Last week, 1,300 police mounted a military-like invasion of a large shantytown called the Complexo de Alemao and killed 19 suspected criminals.

"It's too risky to hold a show for 700,000 people on the eve of the Pan American games and at a time when police are engaged in frequent battles in the Alemao," Tarin said in a statement released by her office.

Concert organizers confirmed the show was suspended but said they would contest the order and expected to overturn it. Brazil's court system has many avenues for appeals, and decisions are frequently changed within hours or days.

"We're negotiating, and expect to reverse the decision," said Vanessa Vascouto, a spokeswoman for the Rio event.

Organizers did not get the required approval of the Rio state police, and the prosecutor plans to appeal the case if the suspension order is overturned, said Daniel Brunet, a spokesman for Tarin.

Tarin last year imposed restrictions on a free concert by the Rolling Stones on Copacabana Beach that drew 1 million people.

At the time, she told the newsweekly magazine Veja that Copacabana is not appropriate for huge concerts because the setting makes it difficult for police to craft "the slightest viable security plan."

Rio's concert would include performances by Lenny Kravitz, Macy Gray, Pharrell Williams, MV Bill and Jorge Ben. The event is the only free concert for Live Earth, founded by Kevin Wall, an Emmy-winning concert producer.

Proceeds from the other concerts will go toward the Alliance for Climate Protection, a non-profit organization chaired by Gore.

Wall was inspired to put on Live Earth after seeing An Inconvenient Truth, Gore's Academy Award-winning documentary on climate change.