In a motion in United States District Court in Manhattan, Sotheby’s, as part of its effort to have the case dismissed, accused federal officials of blocking a $1 million private deal that might have provided for the amicable return of the statue and other improprieties.

In response, prosecutors took the unusual step of accusing a former colleague, Jane A. Levine, who is now a top Sotheby’s executive, of providing “false and misleading information” to the government early in the 30-month investigation. Sotheby’s denied the accusation.