SYDNEY (AP) Australia's two-match series in the United States to face the Women's World Cup champions has been called off as negotiations continue over a new collective bargaining agreement, the player's union said Wednesday.

Spokesman Beau Busch of Professional Footballers Australia, a union representing both male and female players, said the tour was called off late Wednesday afternoon, a day after players refused to show up at a practice session in Sydney.

Football Federation Australia chief executive David Gallop had earlier said the series was ''looking very unlikely'' because of the players' actions.

More from FoxSports

On Wednesday, Gallop said 60,000 seats had been sold for the matches in Detroit on Sept. 17 and Birmingham, Alabama, on Sept. 20.

The union is seeking an increase in wages, international match payments, improvements in accommodation and other benefits for the women's team.

The men's national team boycotted community events before a World Cup qualifier in Perth last week.

Professional Footballers Australia chief executive Adam Vivian said each women's team player makes 21,000 Australian dollars ($14,475) a year.

''They don't even have yearly contracts, they have six-month contracts,'' Vivian told Australian Broadcasting Corporation radio Wednesday, adding that the female players have not been paid in two months.

''When they were negotiated it was because it was on the premise that they were part time, only 120 days a year they would have to work and clearly as we saw in the lead up to the Women's World Cup,'' Vivian said. ''While it was fantastic that they had a full-time program, the remuneration wasn't (great) ... they ended up working 154 days in about six months and so they fall into sort of that underpaid category very quickly.''

The Matildas lost to Japan in the quarterfinals at the Women's World Cup in Canada.

The PFA is also negotiating for more pay for domestic A-League players and an increase in each of the 10 team's salary caps.

''It's sad that the Matildas have been dragged into a dispute that's primarily about the A-League,'' Gallop said Tuesday. ''The offer to the Matildas would basically double their pay over the next four years. The new demands are simply not affordable and the PFA knows it.''