The Premier League would only be allowed to take their games to America if Fifa permits them, according to the chief of the US Soccer Federation.
The Premier League wants to play matches abroad in 2010-11
The comments follow the announcement that the English body is considering other countries hosting its games.
"We've been reluctant to have official games played in the US," US Soccer chief Sunil Gulati told BBC Sport.
"We'll be guided by Fifa on this matter. But if it's not in line with its rules then we won't sanction it."
The Premier League's proposal to have a 39th round of games has aroused widespread criticism, but chief executive Richard Scudamore has remained defiant, insisting that the extension would have a positive rather than negative effect of the sport.
"Clearly, there are a lot of hurdles to overcome," he told the BBC.
"We've seen how sport is globalising, we compete in the entertainment industry.
We understand it's a global sport but it's about nurturing the home game
US Soccer chief Sunil Gulati
"This is a solidarity move where all 20 clubs want to do it. It benefits all of them and it's far better we all do it rather than allow single clubs to."
Gulati, the president of the US Soccer Federation, said he had read about the proposals but that his federation had yet to be approached by the Premier League.
The US Soccer chief added that he was unsure whether acting as hosts would help the growth of football in his own country.
"We had a similar proposal 10 years ago when a team playing in Los Angeles wanted to play in the Mexican league," he said.
"We didn't let that happen and Concacaf (the Confederation of North, Central American and Caribbean Association Football) said no.
"We understand it's a global sport but it's about nurturing the home game.
"If Fifa said 'OK, it's up to the relevant FA's, then we would look at the Premier League proposal.
"We've got a great relationship with the English FA and there's a lot of good reasons to look at it.
"But there are also some issues that we've got which would cause us to be very hesitant."