South Korean volleyball superstar Kim Yeon-koung is threatening to retire from the national team unless she is released from a contract by her former club team Heungkuk Life Insurance.

The 25-year-old Kim was the Most Valuable Player at the London Olympics and is considered one of the top players in the world. She has been an integral part of the South Korean team for several years. The root of the ongoing dispute lies in the contract language that ties her to Heungkuk for six years.

The 192-cm outside hitter played for the Seoul-based team for four years before joining the JT Marvelous in Osaka in 2009 for two seasons. After two campaigns in Kansai, Kim signed with Turkish powerhouse Fenerbahce.