The league's newest expansion team, the Philadelphia Union, starts next season and will play its home games at a stadium being built in Chester. "And we don't have any plans for a roof," Union president Tom Veit said last night.

"We have to manage our league in a way so that we can continue this careful growth but at the same time satisfy the requests and - in many cases - the requirements of the world governing body," MLS commissioner Don Garber told the Associated Press. "FIFA's goal is to work with us to turn this country into a valuable soccer nation and a passionate one. In order to do that our league does need to be closer to the sport internationally."

Key to achieving that will be building more stadiums with roofs to protect against the worst of the American winter, Garber said.

"We play across a continent of 300 million people, across [four] time zones and weather that varies from zero to 30 degrees [Celsius] at any given point," Garber said. "It's impossible to think we can be playing games in December outdoor in Toronto or Boston or New York or Denver, where it can be well below freezing with a foot of snow on the ground. So we have to evolve to get closer to that calendar.

FIFA president Sepp Blatter has expressed concern about the inability of the MLS to rival the top European league since its inception in 1996, two years after the Americans last hosted the World Cup. The U.S. is bidding to host either the 2018 or '22 World Cup at the vote in December 2010.

While accepting that standards are rising in the MLS, Blatter has stated regularly that it needs to switch to Europe's August-May schedule, rather than its current March-October to entice top players.

"Perhaps we have to start thinking about roofed stadiums at some point. But do we have to have a fan base that is developed enough to be immune to the weather, like they do for American football, where they will come out to watch a game regardless of the climate?"