ATHENS (Reuters) - Greece said it would spend 10 billion euros to buy back bonds in a bid to reduce its ballooning debt and unfreeze long-delayed aid, setting a price range above market expectations to ensure sufficient investor interest. The bond buyback is central to the efforts of Greece's foreign lenders to put the near-bankrupt country's debt back on a sustainable footing, and its success is essential to unlocking funding Athens needs to avoid running out of cash. ...