Aug 9 (Reuters) - Former champion Andy Murray has been added to the main draw of the U.S. Open following the withdrawal of Swiss Stan Wawrinka, tournament organisers said on Monday. Murray, who had hip surgeries in 2018 and 2019, has only played a handful of ATP Tour-level events this year having missed the Australian Open because of a positive COVID-19 test and opting out of competing at the French Open. The 34-year-old Murray reached the third round at Wimbledon but withdrew from the men"s singles tournament at the Tokyo Olympics on the advice of his medical team, dashing his hopes for a third consecutive gold medal. Murray, who won the first of his three career Grand Slam titles at the 2012 U.S. Open, did represent Britain in the men"s doubles event in Tokyo where he lost in the quarter-finals. At last year"s U.S. Open, Murray suffered a straight-sets loss in the second round to Canadian Felix Auger-Aliassime. Wawrinka, who captured the last of his three career Grand Slam titles at the 2016 U.S. Open, withdrew as he continues to recover from foot surgery. The 36-year-old former world number three underwent an operation on his left foot this year and has not played on the tour since an opening round defeat at the Qatar Open in March. The U.S. Open runs from Aug. 30-Sept. 12.