Speaking at the launch of the Foundation for Sports Integrity, the 36-year-old said her own campaigning had made her feel like an outcast.

"I’d welcome more players to stand up and speak out, but unfortunately there’s pressure," said Solo. "You can see what happened in my case where I fought for equal pay."

The double Olympic gold medallist has not featured for the US since being suspended for calling opponents Sweden "a bunch of cowards" for playing defensively at the Rio Games in 2016.

A new deal through 2021 was agreed last year bringing improved base pay and bigger bonuses for the US Women's team but it still does not guarantee parity with the men's national team, even if they get the same per diems.

"There’s a law in America that says you cannot discriminate based on gender, but we still have discrimination everywhere you look," said Solo, who recently stood unsuccessfully for president of the US federation.

The US men's team have failed to qualify for the World Cup finals starting in Russia next month while the women's team are world champions and have won three of the seven tournaments to date.

The women have also won four Olympic gold medals and a silver from the six Games since their competition was added to the programme in 1996.

Solo, who joined four high profile players in filing a complaint in 2016 to the US Equal Employment Opportunity Commission, said some others were privately supportive but reluctant to take a stance in public.

"Ultimately they want to remain playing on the US team, so I became kind of the outcast," she said.

"I understand. We have young players, players who more than anything are passionate about the game. They want to play World Cups and Olympics. They want to represent the country.

"But these issues are so much bigger, and the way the world is going... it’s a time for women’s empowerment. You’ve seen women in more leadership roles yet it’s still against a backdrop of inequality and male chauvinism and sexism."

Australian businessman Jamie Fuller, who chairs the foundation, said its aim was to restore integrity in sport through exposing and confronting corruption and unethical behaviour.