Former US vice president Al Gore will provide the political message, urging a potential audience of two billion to lobby industry and governments to take action.

"We're going to ask the two billion people estimated to be in the audience Saturday to take a seven-point pledge that is designed to change behaviour and also to put pressure on political leaders in every country across the ideological spectrum," Gore told NBC television.

The festivities start at 0200 GMT Saturday in Sydney, which passes on to Tokyo, then Shanghai, Hamburg, London, Johannesburg, New York and wrapping up in Rio de Janeiro, with a symbolic rendezvous in Kyoto, Japan and a base in Antarctica.

Some 7,000 events in 129 countries including the eight giant concerts are being promoted by Gore as part of his passionate bid to focus attention on the dangers of climate change.

Gore announced yesterday that Washington had been added as a new location, four months after some members of US President George W Bush's Republican party resisted attempts to hold a concert in the nation's capital.

"I'm happy to announce here on CNN that a surprise new concert venue is going to be the Mall in our nation's capital," Gore told the cable network, referring to the sprawling green space near the Congress.

According to Gore, the scaled-down Washington event would be a daytime concert at the National Museum of the American Indian's outdoor plaza, kicking off at 10 am (1400 GMT) and featuring country music stars Trisha Yearwood and Garth Brooks.

Gore also told CNN all the artists would perform for free.

"These are the best acts in the entire world, and they've all said, yes, we're going to give our time and our talents in order to try to help save the climate," he said.

The Rio concert was nearly nixed by a judge who feared for the safety of the 700,000 expected to attend the free concert in Copacabana featuring Macy Gray, Lenny Kravitz, Pharrell Williams and Xuxa.

A concert for Istanbul was called off due to security reasons.

Bob Geldof, organizer of the 1985 Live Aid concert that set the standard for world activism through music, has expressed doubts that Live Earth would be more effective than pressing government and industry to action.

But Gore called the concerts "an SOS, a wake-up call to the entire world. And it will launch a three-year global campaign to get the facts out to everybody in the world" through his Alliance for Climate Protection.

"People will be aware of the facts but they will connect that awareness to what we can do to solve it," he told NBC.

Gore's Academy Award-winning documentary "An Inconvenient Truth" argues that human activity is raising the Earth's temperature, threatening changes in weather patterns, the seas and endangering life on the planet.

His crusade against global warming has prompted calls for him to enter the 2008 US presidential race after having narrowly lost the 2000 vote. But he told NBC: "I don't expect to be a candidate again, ever.

"I'm involved in a different kind of campaign to try to raise awareness of what I truly believe is the most serious crisis our civilization has ever faced."

At Wembley Stadium in London, musical acts will include the Red Hot Chili Peppers, Duran Duran, Foo Fighters, Black Eyed Peas and John Legend.

The Police, Smashing Pumpkins, Kanye West, Alicia Keys, Jon Bon Jovi, Roger Waters and Gore will take the stage at Giants Stadium outside New York.

Angelique Kidjo, Joss Stone and UB40 will play in South Africa.

Shakira, Snoop Dogg and Yusuf Islam (formerly Cat Stevens) will play at Hamburg and Linkin Park will play Tokyo.

The concerts aim to promote action to fight global warming, caused by the release of gases into the Earth's atmosphere, allowing light in but preventing heat from escaping, much like the glass in a greenhouse.

Gore preaches energy conservation and lower "greenhouse gas" emissions, such as was agreed in the 1997 Kyoto Protocol which was signed but not ratified by the United States.

Performances will be carried on national television networks around the world and on the Internet at http://liveearth.msn.com.