Britney Spears left Conway Studios after a couple hours in Los Angeles, August 21,2008.
The pair were supposed to collaborate on a track for Britney's last LP "Blackout" but she missed the recording session scheduled at producer Timbaland's studio.
At the time, a source claimed Britney "just didn't show up". Britney's father Jamie -- who is currently acting as co--conservator of her estate -- is said to be keen for one time sweethearts to reunite.
Earlier this year, it was reported Jamie had asked Justin to perform with Britney, but the "Sexy Back" singer had refused.
At the time, a source said: "Jamie wanted Justin to help Britney. For a time Justin seriously considered doing a couple of concerts with her to help her out."
As well as a duet with Justin, Britney's next album is set to include a song she has written about her sons -- Sean Preston, two, and 23-month-old Jayden James. The troubled star revealed: "I've written a song for my next LP about them called 'My Baby'. It's a beautiful song, I'm really proud of it."
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