Celine Dion\'s doctors say she must rest her voice until the end of April, prompting the Canadian entertainer to cancel her spring shows in Las Vegas. The Colosseum at Caesars Palace, the venue at which Dion was to perform through March 18, said Tuesday the concerts have been canceled due to Dion\'s illness. A run of performances from June 9 through Aug. 19 are to proceed as scheduled, however. Dion canceled her show\'s last weekend because she was suffering from laryngitis. She was diagnosed Monday with weakness in her right vocal chord, secondary to a viral illness. Her doctors recommended she rest her voice for six to eight weeks to ensure a complete recovery. \"I tried to sing at my sound-check last week, and I had no control of my voice whatsoever,\" Dion said in a statement Tuesday. \"We thought that after a few days rest I would improve but it wasn\'t getting any better... I guess it was worse than I thought. ... Obviously, this is the worst thing for a singer.... not being able to do your shows. I feel worse knowing that I\'m disappointing my fans. I\'m so sorry... I hope they forgive me.\" Those who purchased tickets with a credit card for the canceled performances will be automatically refunded. Those who bought tickets with cash may present tickets at the original point of sale for a refund.