The U.S. Soccer Federation has sued the union of its World Cup-winning women's soccer team, saying it fears that players may attempt to strike ahead of this year's Olympics.

The lawsuit was filed in Chicago federal court Wednesday. In a statement, U.S. Soccer said it "reluctantly" filed the suit to "confirm the existence" of a collective bargaining agreement with the union representing the U.S. women's national team.

The USSF alleges that Richard Nichols, the executive director of the Women's National Team Players Association, does not believe there is a current CBA in place.

The federation maintains that an agreement -- composed of the 2005 CBA and augmented by a memorandum of understanding -- took effect in 2013 and is still valid until Dec. 31.

In a Jan. 6 email attached to the lawsuit, Nichols told the USSF the union's position was that the collective bargaining agreement no longer exists and the 2013 memorandum of understanding could be terminated at any time.

Nichols told ESPN FC that he was disappointed that U.S. Soccer took the matter regarding the CBA to court.