U.S. singer-songwriter Neil Diamond, one of pop music's all-time best-selling artists, has been diagnosed with Parkinson's disease and plans to retire from touring, his official website said on Monday.The onset of the disease has made it difficult for him to travel and perform on a large-scale, a statement on the site said, adding he will be canceling upcoming concert dates in Australia and New Zealand and offering refunds."It is with great reluctance and disappointment that I announce my retirement from concert touring. I have been so honored to bring my shows to the public for the past 50 years," Diamond said in the statement, offering apologies to those who purchased tickets to his upcoming shows.Diamond, known for hits including "Sweet Caroline" and "Cracklin' Rosie," said he plans to remain active in song writing and recording.Later this week, Diamond will turn 77 and on Sunday the Recording Academy plans to honor him with its Lifetime Achievement Award.Diamond has sold more than 130 million albums worldwide and 38 of his singles have made it to the Top 40, according to the academy.Grammy-award winner Diamond, a fixture in American pop music since he began recording in the 1960s, has been inducted into the Rock and Roll Hall of Fame."My thanks goes out to my loyal and devoted audiences around the world. You will always have my appreciation for your support and encouragement," Diamond said."This ride has been ‘so good, so good, so good’ thanks to you," he said.