RIO DE JANEIRO, Brazil -- A Brazilian judge has canceled Saturday's Live Earth concert in Rio de Janeiro because of security concerns.

A prosecutor said there are not enough police officers to ensure the safety of a concert that could draw up to 700,000 people.

The Rio de Janiero show is the only Live Earth concert that is free. Lenny Kravitz, Pharrell Williams and Macy Gray are part of the lineup.

Concert organizers say they are trying to overturn the judge's order.

The Live Earth concerts, organized by former Vice President Al Gore, will be held Saturday at locations around the world to draw attention to global warming.

The concerts will take place around the clock and bring together more than 150 music artists and 2 billion people, organizers said.

Acts in Hamburg, Germany, include Enrique Iglesias, Shakira and Snoop Dog. Jack Johnson and Crowded House are slated to appear in Sydney, Australia. Madonna, Beastie Boys, Duran Duran, Black Eyed Peas and John Legend are on tap for London. And in New York, Akon, Bon Jovi, Dave Mathews Band, Kanye West, Ludacris and The Police are among those scheduled to appear.

Scientists stationed in Antarctica are also scheduled to play music as part of the event.

Microsoft is an official online partner with Live Earth. Other partners include Philips, ABSOLUT, Pepsi, Stonyfield Farm and Verisign.

For more information visit Live Erath/Brazil.