Forty top women football players have signed a petition urging FIFA to change its proposal for the 2015 Women's World Cup, in Canada, to be contested on artificial pitches instead of grass, considering it to be a discriminatory proposal.

The World Cup finals for men and women, contested every four years, have always been played on natural grass. Players and coaches believe there is a higher risk of injury on artificial turf and that it causes more wear and tear on athletes' bodies.

Players threaten legal action
In a three-page letter dated July 28 to FIFA and the Canadian Soccer Association, lawyers representing players from Germany, Brazil, Mexico, Spain, the United States, New Zealand and Costa Rica, among other countries, said: "The proposal is discriminatory and violates Canadian law."

"If your organisations will not engage in a meaningful dialogue on how to correct the discriminatory treatment of women players, we are prepared to pursue legal action which we are confident should succeed," the letter said.

A FIFA spokesman confirmed the letter had been received, but declined to comment. The Canadian Soccer Association also declined to comment and referred enquiries to FIFA.

In the letter, the players, who include Abby Wambach of the United States and Germany's Nadine Angerer , FIFA players of the year for 2012 and 2013 respectively , said they can suggest "several affordable ways" to host the tournament on grass.

One of the lawyers for the group of players, Hampton Dellinger of Boies, Schiller & Flexner in Washington, D.C., said that while all legal avenues will be pursued to convince the World Cup authorities to provide grass surfaces, a boycott is not on the table.

"Canada has very robust human rights statutes, both the provincial codes and the national charter, that ban discrimination based on gender, and I don't think there can be any question but that this relegation of women to a second-class surface is based on gender," Dellinger said.

'You've got to question why Fifa awarded it to Canada'
The 2014 FIFA World Cup for men in Brazil was played on grass and there are no plans to shift future men's tournaments to artificial turf.

Some professional football leagues and FIFA World Cup age-group matches are played on artificial turf, including a number of the 2014 FIFA U-20 Women's World Cup matches, which kicked-off, in Canada, last Tuesday (5 August).

Canada will host the Women's World Cup in June and July 2015 in six cities - Vancouver, Edmonton, Winnipeg, Ottawa, Montreal and Moncton, where stadiums with artificial turf predominate.

"These pitches slow the game down, the ball bounces differently and there are more injury consequences.

"I can't believe there aren't enough grass pitches to host World Cup games in Canada. You've got to question why Fifa awarded it to Canada in the first place if that was the case." said England captain Faye White to the BBC.