will.i.am praises Jackson's vocal ability

will.i.am has praised Michael Jackson's vocal ability and assured fans that he will be fit for his upcoming London residency.

The Black Eyed Peas star, who has recently recorded material with Jackson, claimed that his voice is better than many other artists around.

"He's doing both voice testing just to sing for five minutes. He's testing his voice for three hours to sing for five minutes," he told Starpulse.

"Fergie don't do that s**t. Usher don't do that s**t. None of the people that you think still got it do that. I've seen it, in my house.

"That's because he's a perfectionist and he just likes testing his voice. I've seen it... Perfect pitch."

Recent reports suggested that Jackson was being "ordered" to gain weight ahead of his live shows.

Jackson kicks off his seven-month residency at London's O2 arena on July 8.