All 28 members of the US women's national team filed a discrimination lawsuit against the US Soccer Federation (USSF) on Friday, just three months before defending their World Cup title.

US midfielders Carli Lloyd and Megan Rapinoe, who helped the Americans capture the crown in Canada four years ago, and have them atop the world rankings headed into the 2019 tournament in France, were among those suing the national governing body in US District Court in Los Angeles for equal pay and working conditions to their less successful male counterparts.

"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 lawsuit said.

"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."

US teams have taken the Women's World Cup title three times, including the inaugural 1991 edition in China, the 1999 event on home soil and in Canada four years ago.

US men, by comparison, were third in 1930 in the first World Cup but their best showing since was a quarter-finals loss in 2002.

US women players seek millions of dollars in back pay and damages and have long argued the inequalities compared to men include quality of venues, number of matches, medical treatment, coaching and training opportunities and transportation.

Issues include when US women called off a 2015 match in Honolulu on articifical turf due to safety worries over poor field conditions.

"Celebrate each other," US star Alex Morgan, also in the lawsuit, tweeted Friday with a photo of the US team training and the message: "Women around the world: Supporting each other, Fighting for each other, Showing up for each other, Empowering each other."

The women seek class action status to include every woman who has played on the national team since February 2015, which could add dozens more players to the lawsuit.

"The USSF has utterly failed to promote gender equality," the women claimed in the lawsuit. "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, in fact, has admitted that it pays its female player employees less than its male player employees and has gone so far as to claim that 'market realities are such that the women do not deserve to be paid equally to the men.'

"The USSF admits to such purposeful gender discrimination even during times when the (women) earned more profit, played more games, won more games, earned more championships, and/or garnered higher television audiences."

US Soccer has previously noted its support of the National Women's Soccer League as a way of backing US women's players in a way not done for men.

The US women, who finished second to England in the just-concluded SheBelieves Cup tournament at American venues, are set to defend their crown June 7-July 7 at the Women's World Cup in France.

The Americans are in Group F with Thailand, Chile and Sweden for the first round. The US women open against Thailand on June 11.

The move, coming on International Women's Day, is the latest in a years-old dispute between players and the federation, which included a wage discrimination complaint with the Equal Employment Opportunity Commission in 2016, the players saying the USSF has spent more on training and salaries for men despite talk of investing in greater opportunities for women.

"The USSF... has paid only lip service to gender equality and continues to practice gender-based discrimination against its champion female employees," the lawsuit said.

US men and women each have collective bargaining agreements with the USSF, the women's deal being signed to avoid a possible strike ahead of the 2016 Rio Olympics. It expires at the end of 2021.