Jan 7 (Reuters) - Two-time national champion Alysa Liu has withdrawn from the U.S. Figure Skating Championships after testing positive for COVID-19 and plans to petition for one of three spots on the U.S. Olympic team, U.S. Figure Skating said on Friday. Liu was in third place on Thursday after earning a score of 71.42 in the women"s short program in Nashville. She will miss Friday"s free skate as a result of the positive test. Liu is the latest high-profile U.S. skater to withdraw from the championships after the pairs team of Alexa Knierim and Brandon Frazier were forced to withdraw from the competition after Frazier contracted the virus. Knierim and Frazier are also petitioning for one of two spots on the team that will head to next month"s Beijing Winter Games. The final team will be named after the competition wraps up this weekend.