(CNN) Members of the top-ranked US women's national soccer team on Friday -- about three months before the upcoming World Cup -- filed a federal class-action lawsuit against the US Soccer Federation citing gender discrimination, according to court documents.

Twenty-eight members of the team are listed as plaintiffs in the suit, which was filed in US District Court in California where the women are employed when they gather for national team camp.

The suit states that the women filed on behalf of themselves and all other similarly situated current and former women's national team players "who the USSF has subjected to its continuing policies and practices of gender discrimination."

The suit alleges that the federation discriminates by paying the women less than members of the men's national team "for substantially equal work and by denying them at least equal playing, training, and travel conditions; equal promotion of their games; equal support and development for their games; and other terms and conditions of employment equal to the MNT."

US Soccer did not immediately respond to a CNN request for comment.

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