Michael Jackson made a musical comeback of sorts Wednesday, singing his charity single We Are The World among a group of swaying, clapping kids -- until the sound cut out inexplicably as he struggled for the high notes.

The 2006 World Music Awards in London was honoring him with an award commemorating the 25th anniversary of his hugely popular album Thriller.

The 48-year-old singer, performing live for the first time since he was acquitted of child molestation charges in June 2005, had been expected to sing his seminal hit Thriller.

But to the huge disappointment of screaming fans, that was performed instead by young American star Chris Brown.

"There have been so many people who have loved me and stood by me. I love all the fans from the bottom of my heart," Jackson said before flinging his black jacket into the crowd and exiting the stage.

The failure of the deposed King of Pop to demonstrate his voice is likely to raise further doubts about his ability to resurrect a career that has been on hold for years.

"I would say there's very little chance of him coming back from where he is," said Gareth Grundy, deputy editor of the Q music magazine.

"I think people will always be fascinated by the freak show, and that's what's going on," he said. "I would categorise him as a celebrity as opposed to an artist," he added.

Earlier in the evening, Jackson was given the Diamond Award honoring artists who sell more than 100 million records.

Jackson's Thriller album won eight Grammy Awards and sold more than 50 million copies.

Editor: Donald