Kevin Federline Not Signing Divorce Agreement

Under an agreement reached in March, the two celebrities would continue their joint custody of their two children.  However, a source tells People magazine that Federline is not sure he wants to sign off on that earlier agreement.  "Britney’s attorneys are anxious to see Kevin sign off on a divorce," the source says. "But Kevin and his lawyer Mark Vincent Kaplan are dragging their heels out of concern over reports of Britney’s post-rehab partying."

Federline’s camp, the source adds, "wants to make sure that the divorce document makes it simple enough for Kevin to downsize Britney’s access to her kids the next time her behavior troubles him."

Spears, 25, and Federline separated at the end of last year.  Since then, the Toxic singer has entered a rehabilitation clinic.