A group of 13 members of the U.S. Senate have urged FIFA to switch next year's women's World Cup in Canada to natural grass saying the decision to play on artificial turf was a "short-sighted and counterproductive decision".
Over 40 international women's players have filed a lawsuit in Canada against local organisers and FIFA claiming that is discriminatory to play a women's World Cup on artificial turf when the men's tournament is always held on grass.
The bipartisan group of US Senators - led by Ohio Democrat Sherrod Brown - also wrote to US Soccer President Sunil Gulati urging him to use his influence on FIFA's Executive Committee to bring about a change in policy.
"Artificial turf both increases the risk of serious injury and fundamentally changes the way the game is played. FIFA has never used turf fields for the men's World Cup," the senators wrote in the letter to Blatter.
"As members of the United States Senate, we are deeply concerned with FIFA's treatment of these players. We urge you to begin good faith negotiations with these athletes, free of retaliation and with the equal treatment that they deserve," they added.
The senators' stance was welcomed by US international Abby Wambach, who has been a leading voice against artificial turf at next year's World Cup.
"We're grateful that these Senators are standing beside us in our fight for an equal playing field at the World Cup," said Wambach in a statement. "But what's at stake here is more than just the surface we'll be playing on - it's about gender equality and standing up for what's right."
FIFA denies that there is any discrimination with officials arguing that the fields have passed their standards checks.
On Friday, FIFA distributed an interview with Jan Ekstrand, former team doctor of the Swedish national team, a vice-chairman of the UEFA Medical Committee and a professor in Sports Medicine.
Ekstrand says there is no greater risk of injury on artificial surfaces.
Meanwhile, a group of top female players will head to mediation with the Canadian Soccer Association in a bid to resolve the turf war.