US Women's National Team sues soccer's governing body for gender discrimination on International Women's Day U.S. Soccer "has utterly failed to promote gender equality," the suit claims.

Athletes on the world champion U.S. Women's National Team sued the United States Soccer Federation (USSF) Friday for gender discrimination, blasting the sport's governing body for allegedly paying mere "lip service" to gender equality and dishing out markedly more pay to the decidedly less successful men's team.

The scathing lawsuit, filed in California federal court on International Women's Day, comes after years of public battles from the USWNT for equal pay and conditions and three months before the team is scheduled to begin competition at the FIFA World Cup, where they will be returning as defending champions.

"In reality, the USSF has utterly failed to promote gender equality," the lawsuit reads. "It has stubbornly refused to treat its female employees who are members of the [women's national team] equally to its male employees who are members of the [men's national team]."

The USSF, the lawsuit claims, "has paid only lip service to gender equality and continues to practice gender-based discrimination against its champion female employees on the WNT in comparison to its less successful male employees on the MNT."

"Despite the fact that these female and male players are called upon to perform the same job responsibilities on their teams and participate in international competitions for their single common employer, the USSF, the female players have been consistently paid less money than their male counterparts," the suit says.

"This is true even though their performance has been superior to that of the male players – with the female players, in contrast to male players, becoming world champions." (p. 1)

The U.S. men's soccer team did not qualify for the 2018 FIFA World Cup. Their best finish was third place -- in 1930. The U.S. women's team, on the other hand, has won the World Cup three times -- in 1991, 1999 and 2015 -- and the gold medal at the Olympics four times, most recently in 2012.

The 28 members of the 2015 winning team are all named as plaintiffs, including stars Alex Morgan, Megan Rapinoe and Carli Lloyd, and the suit requests class action status to represent players who have been on the team since February of that year.

The WNT earned more than three times less than the MNT while performing demonstrably better.

The suit seeks back pay including interest and benefits, damages, attorneys' fees and other relief.

The suit says that female players earned $15,000 for making the World Cup team in 2013. On the other hand, men earned $55,000 for making the team in 2014 and $68,750 in 2018. (p. 12)

"The pay for advancement through the rounds of the World Cup was so skewed that, in 2014, the USSF provided the MNT with performance bonuses totaling $5,375,000 for losing in the Round of 16, while, in 2015, the USSF provided the WNT with only $1,725,000 for winning the entire tournament," the lawsuit reads. "The WNT earned more than three times less than the MNT while performing demonstrably better." (p. 12)

The lawsuit cites not just pay, but also the denial of "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."

In 2015, athletes complained about playing conditions after Rapinoe tore her ACL during training on a grass field that was reportedly described as being in bad shape. U.S. Soccer then canceled a match in Honolulu as its turf was "not suitable."

[The USSF

That the women's team, but not the men's, was subjected to playing on turf fields was a regular issue between athletes and U.S. Soccer.

In 2017, the women's team reached an agreement with the USSF after filing a complaint with the United States Equal Employment Opportunity Commission over pay.

The agreement included direct and bonus pay increases and per diems equal to the men's team, according to ESPNW, as well as improved travel and financial support for pregnant or adopting players. It also included required improvements in National Women's Soccer League standards.

In February, the EEOC issued the soccer players a "right to sue," the new lawsuit indicates, which is required to sue for discrimination under federal law.

The USWNT is not the only women's team fighting for equal pay and conditions. The women's national hockey team has been on its own mission, following the soccer team and spurred by its victory at the 2018 Winter Olympics.

Similarly, the WNBA and tennis players have also been making calls for equal pay, prize money, conditions and infrastructure.

U.S. Soccer told ABC News it does not comment on ongoing legal matters.