Def Jam's Kevin Liles has resigned from his position as president of the label, after negotiations between the mogul and parent company Universal Music Group broke down.According to The New York Post, the two sides could not reach an agreement on a contract extension.The negotiations broke down over money.Last week, Island/Def Jam's CEO Lyor Cohen left the label for Warner Music Group."Kevin has been in negotiations with Warner as well," a source close to the negotiation process told AllHipHop.com. "They were both being courted by Warner."The source added that Liles will most-likely head to Warner Music Group as well.Liles will remain at Island Def Jam until March. He is penning a book about hip-hop management, which is due in stores in 2005.