Five senior members of the World Cup-winning US football team have filed a complaint against the national federation for wage discrimination.
Alex Morgan, Carli Lloyd, Megan Rapinoe, Becky Sauerbrunn and Hope Solo say they are paid less than half of what the male USA players receive.
"The numbers speak for themselves," said goalkeeper Solo in a statement.
The US Soccer Federation said it was disappointed, given the work it had done in building the women's game.
American women's football has dominated the international game in recent decades, with a string of titles.
"We are the best in the world, have three World Cup Championships, four Olympic Championships, and the USMNT [men's team] get paid more just to show up than we get paid to win major championships," said Solo.
Her team-mate Lloyd, who was named the best player at last year's World Cup, said they had been patient over the years in waiting for action to deliver fair pay.
Former Everton and LA Galaxy winger Landon Donovan - who won 157 caps for the US men's team - tweeted his support for the women's team's cause.
"#USWNT absolutely deserve to be treated fairly in all ways," he said.
"Important to remember that these issues are/can be collectively bargained."
US Presidential candidate Hillary Clinton said: "Wouldn't want to face these women on the field or in the courtroom. Every woman deserves equal pay."
The complaint against the US Soccer Federation was filed with the Equal Employment Opportunity Commission on Thursday morning.
One of the lawyers representing the players, Jeffrey Kessler, said the women's game generated more income for US Soccer than the men's and it was time to address the "discriminatory and unfair treatment'' they have endured for years.
The five players were acting on behalf of all the players, he said.
There has been an ongoing legal battle between the federation and the players' union over collective bargaining.
A statement from US Soccer said it had not yet seen the complaint.
But it added: "We have been a world leader in women's soccer and are proud of the commitment we have made to building the women's game in the United States over the past 30 years."
Clarification: An earlier version of this story said the women players filed a lawsuit against the US Soccer Federation. They have actually filed a wage-discrimination action against USSF with the Equal Employment Opportunity Commission.