Players have reported for duty with Spain's women's national team with the threat of a fine or a domestic ban looming over them if they don't.

The six Madrid-based players arrived at a hotel in the Spanish capital on Tuesday before departing for Valencia, where the rest of the squad are expected to join them to prepare for UEFA Nations League games against Sweden and Switzerland.

Twenty of the 23 players called up by new Spain head coach Montse Tome on Monday had released a statement on Friday saying they were unwilling to play for the national team until changes were carried out by the Royal Spanish Football Federation [RFEF].

The players, many of whom helped La Roja win the World Cup last month, said they were surprised by their call-up on Monday after they had made clear their decision not to play for Spain until their demands for change were met.

However, according to Spanish sports law, athletes are required to answer the call of their national team unless there are circumstances that impede them from playing, such as an injury.

Should they refuse the call, the players face sanctions including fines of up to 30,000 ($32,000) and the suspension of their federation licence for two to 15 years.

Victor Francos, the president of the supreme council for sports in the country [CSD], said he hopes it does not come to that and plans to act as a mediator between the players and the RFEF.

"If the players don't show up, the government will do what it has to do, which is to apply the law," Francos said. "Unfortunately, the law is the law, but I still hope that there can be a solution. I am going to talk with the players. I am going to try."

Miquel Iceta, the minister of culture and sport, said he cannot imagine the players being sanctioned and called on the RFEF to make the necessary changes.

"The RFEF does not have the right to deprive Spain of the women's national team, especially after they have won the World Cup," Iceta said.

"We call on the RFEF to enact structural changes to ensure the federation is a safe, competitive, professional space.

"I can't even imagine [sanctions.] We are going to find a solution. What cannot happen is that injustices continue to be committed which harm the players who have given the best of themselves and won a World Cup for the first time in history.

"We have to get back on track and live up to what society demands and to what the players have earned."

Spain's players first pushed for change at the RFEF last September when 15 players made themselves unavailable for selection until certain improvements were met.

Three of the 15 eventually returned for the World Cup, which ended with Spain beating England in the final in Sydney, but federation president Luis Rubiales' conduct after that game has re-opened the dispute.

Rubiales, who has since stepped down following an outcry, is facing criminal charges for an unsolicited kiss on Jenni Hermoso, while he was also condemned for grabbing his crotch, hugging and kissing some players and throwing another over his shoulders.

When he initially refused to resign, 81 current and retired Spain internationals said they would not play for the national team again under Rubiales' leadership.

Following his resignation, plus the dismissal of coach Jorge Vilda, 39 players, including 21 members of the World Cup winning squad, announced last Friday they were still seeking further changes.

In a statement published on social media, they asked for a restructuring of women's football within the RFEF as well as changes to the president's cabinet, the media and communications department and the integrity department.

Of the 39 signatories, 20 were called up by Tome on Monday. Athenea del Castillo, who was in the World Cup squad, did not sign Friday's letter and said she was ready to play for the national team.

María Méndez and Rosa Márquez are the other two players whose names don't appear, although they have not previously been regulars with the national team.

Hermoso has not been called up and on Monday she hit back at Tome's suggestion that she had been left out to "protect" her after she pressed charges against Rubiales for sexual assault.

"Protect me from what? And from whom?" Hermoso said in a statement.

Spain face Sweden in Gothenburg on Friday and then host Switzerland in Cordoba on Tuesday, Sept. 26. Both games are in the Nations League, which also serves as the qualification pathway for next summer's Olympics.