(CNN) The US Olympic Committee's CEO has asked all members of the USA Gymnastics board of directors to resign, according to a letter obtained by CNN.

Scott Blackmun said USAG will lose its status as a sports governing body unless the board resigns by Wednesday and an interim board is in place by February 28.

Three top USA Gymnastics board members resigned earlier this week , but the Indianapolis-based governing body has 18 other board positions.

Blackmun's request comes in the wake of a scandal over sexual abuse by former national team doctor Larry Nassar, who was sentenced to 40 to 175 years in prison on Wednesday.

"We do not base these requirements on any knowledge that any individual USAG staff or board members had a role in fostering or obscuring Nassar's actions," Blackmun wrote. "Our position comes from a clear sense that USAG culture needs fundamental rebuilding."

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