The individual, who wasn't authorized to speak publicly, told The Associated Press on Thursday that Ballmer and the Sterling Family Trust now have a binding agreement. The deal now must be presented to the NBA.
Shelly Sterling negotiated the sale after her husband, Donald Sterling, made racist remarks that were made public. Donald Sterling must also approve the final agreement as a 50 percent owner. His attorneys say that won't happen.
Ballmer beat out bids by Guggenheim Partners and a group including former NBA All- Star Grant Hill.
The Associated Press contributed to this report
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