Custody of Britney Spears and Kevin Federline's two young sons will be settled in a trial in August, after an attempt to settle out of court failed on Thursday.

The pair spent the day in talks with a mediator, but Federline's attorney Mark Vincent Kaplan has confirmed no agreement could be reached.

He tells E! News, "The mediation didn't result in an agreement that would avoid the trial set in August."

But he insists there was no breakdown in communication between the former couple, adding, "The mood was comfortable, positive and it was a mood that was consistent with opening at least a great dialogue, which is necessary.

"If the existing arrangement was acceptable to both parties... we wouldn't have to go to trial. But that didn't happen."

The trial is due to begin on August 25th, and would result in a final custody ruling.

Kaplan added that Federline is seeking sole physical and legal custody of Sean Preston and Jayden James. Federline was handed full custody of the boys after Spears was committed to a psychiatric facility to treat an alleged bipolar disorder following a stand-off with police and childcare officials in January.