She's been looking back to her best of late, and now she's ready to relaunch her career with a duet with an old friend.

Britney Spears is planning to record a duet with Justin Timberlake, according to US sources.

The pair - who dated in their teens and split in 2002 - will be teaming up for a song on the Toxic singer's next album, which is due at the end of the year.

Britney Spears arrives at the recording studios as she gets ready to relaunch her career

According to the New York Post, the former couple were supposed to team up for her last album, but troubled Spears missed her recording session with Timbaland at the legendary producer's Virginia Beach studio last August. 

'She just didn't show up,' a source said.

The duo with her former flame comes as Spears continues to relaunch her career and as she has been following a strict diet and exercise programme.

She appears on the cover of the latest issue of American celebrity magazine, OK! in a swimsuit - and tells how she has got her figure back thanks to diet and exercise.

She said: "I'm the healthiest I've been all my life.

Britney will be teaming up with former flame Justin Timberlake for a track which will be on her new album

'My diet has a lot to do with my getting into shape. I have no sugar. I don't eat fruit or even fruit juice because of the sugar. 

'I eat chicken and salmon and rice. I eat avocados. I'll have egg whites for breakfast and sometimes turkey burgers for lunch. I try to do just 1,200 calories a day. 

'It may sound like it's not much, but it's actually a lot of food if you eat the right things.'

Britney's mother Lynn and friend, accompany the singer to the recording studio