Three days of celebrations will culminate in an evening concert at London's Hyde Park on June 27 that will feature artists ranging from TV talent show star Leona Lewis to Simple Minds and Annie Lennox.

"You all know that I am supposed to be retired but my friends and the charitable organisations that bear my name want to use my 90th birthday year to raise funds to continue our work and so of course I want to help them," Mandela said.

"So, we have a bargain -- I am going to London and they will host a concert in Hyde Park, which will raise awareness of our continuing work and much needed funds," he added in a statement.

Mandela, the anti-apartheid activist who spent 27 years in prison before being released in 1990, went on to lead South Africa until 1999. Since then he has been involved in charity work, including the fight against AIDS.

Proceeds from the concert will go to the 46664 global HIV/AIDS campaign named after his prison number.

Tickets can be purchased by registering before 1800 GMT on Tuesday at www.46664.com and go on public sale on May 9 at 0900 GMT at www.livenation.co.uk. They cost 65 pounds each.

Mandela turns 90 on July 18.