Bob Geldof has unveiled plans for a repeat of 1985's Live Aid concert, called Live 8, to highlight the ongoing problem of global poverty and debt.
The free event will be held in London's Hyde Park on 2 July with concerts in Philadelphia, Paris, Rome and Berlin.
Madonna and Sir Paul McCartney are among stars playing in London while Stevie Wonder is on the US line-up.
A text message lottery is being held on 6 June to determine who will gain tickets to the UK concert.
Listeners to breakfast shows on BBC and commercial radio stations will be asked to send a text message at 0800 BST containing the answer to a multiple choice question. The winners will get two tickets to the show.
It will also be shown on big screens in seven cities across the UK, and shown live on BBC TV and radio.
WHO IS TAKING PART?
Sir Paul McCartney
Sir Elton John
Will Smith, Bon Jovi, Stevie Wonder and Maroon 5 are among the performers who will play the US city's Cradle of America venue.
Veteran band Duran Duran will play in Rome, while A-ha will perform in Berlin.
Sir Elton John said he was "extremely honoured" to be taking part in the event, which he added will feature "la creme de la creme of musicians".
Geldof said there was a strong possibility that the Spice Girls would reform for the concert.
"I spoke to them this morning. It looks very good. That's all we can say," he told the BBC.
The aim will be to raise awareness of Make Poverty History, a campaign to get the richest nations to cancel debt and increase aid to developing countries, and to promote fair trade.
The G8 summit takes place from 6 to 8 July at Gleneagles in Scotland.
Jamiroquai will perform at the concert in Paris
Some economists were sceptical the aims of the Make Poverty History campaign would help the people it was targeted at.
Kendra Okonski, of the International Policy Network, said debt relief, aid and trade justice had been a "demonstrable failure" for decades.
"Aid has tended to reward failing governments and undermine democracy," she said.
"In the case of Uganda, they're waging an illegal war with aid money that's given by the United States.
"Debt per se is not a bad thing. Lots of us have mortgages.
"If you say all debts are forgiven it actually punishes countries which are doing a good job paying back their debt."
Geldof said the event was "not for charity but political justice", adding that organisers had "scrambled like crazy" to stage the concerts to highlight the plight of Africa.
"This is to finally, as much as we can, put a stop to that," said the political campaigner and musician.
"There is more than a chance that the boys and girls with guitars finally get to tilt the world on its axis," he added.
Jonathan Ross will present the BBC's coverage in the UK, while Graham Norton will report from Philadelphia.
The UK government has backed the project, with Culture Secretary Tessa Jowell saying Live 8 will "set the scene" for the G8 summit.
Meanwhile, the Band Aid Trust has recouped more than £2m in VAT from the government, which was made from DVD sales of the 1985 Live Aid concert.
"We want it to be the biggest and best open air concert that the capital has ever seen," she said.
The original Live Aid concerts, on 13 July 1985 in Wembley Stadium and JFK Stadium, Philadelphia, raised £40m for famine relief in Africa.