June 29 (Reuters) - The world's biggest uncut diamond, Lucara Diamond Corp's Lesedi la Rona gem, failed to sell at a Sotheby's auction on Wednesday after bids fell short of the minimum reserve price, the company said.

As a result, Lucara will be "retaining" the massive 1,109-carat stone, it said in a statement. The tennis ball-sized gem was discovered by the Vancouver-based company in its Botswana mine last November. (Reporting by Nicole Mordant in Vancouver; Editing by Jeffrey Benkoe)