More than 20,000 people have signed an online petition to demand Japan's world champion women footballers be treated equally with their male counterparts when they fly home from the London Olympic Games.

A row over sexism flared after the women were seated in premium economy while Japan's rather less successful under-23 men's squad relaxed in business class on the same plane when they headed to the London Games on July 16.

The social action website change.org said Thursday the petition had attracted more than 20,000 signatures, 12 days after two Japanese women launched the online campaign.

Japan and the US, the defending champions, were set for the women's football gold-medal clash in London later in the day, in a repeat of the World Cup final a year ago.

Petition organizers Sohko Fujimoto and Reina Komiya said the Japan Football Association had promised a business-class return flight would be considered for the women's team if they "bring a medal home."

"But equality between our women's and men's teams shouldn't depend on a medal," said the women.

Women's team coach Norio Sasaki told Japan's Kyodo news agency earlier, "The Japan Football Association is trying to work something out" on the seating.

"The problem is when we go back there will probably not be enough business seats available. If that's the case we will be in premium again."

The Nikkan Sports daily said the association had decided to upgrade all the women to business class.