The United States may have overstepped its boundaries in a recent House bill, prompting Japan to send a letter of concern to U.S. Trade Representative Ron Kirk. Japan contends that the recent House bill – which covered energy use and water conservation — unfairly promoted “Buy American” provisions.

According to the letter, the House bill – which is now on its way to the Senate – unfairly sets the parameters that funds can only be used to purchase vehicles made by the Detroit Three – General Motors, Chrysler and Ford. However, the U.S. says that its “Buy American” provisions don’t violate any of the World Trade Organization’s rules.

“If it limits it to just the three, this violates the World Trade Organization’s fundamental principle of non-discrimination,” an unnamed official told Automotive News.

“Taking into consideration the flow from the previous stimulus package, we are concerned that there will be more moves to promote purchasing of American products.”

The WTO commented on unfair trade practices due to the global economic downturn just this month.

It remains to be seen how the bill will play out, but it seems as though the “Buy American” provisions could be a little outdated. Several foreign automakers have factories setup throughout the United States, in some cases producing vehicles with higher U.S.-made contents than GM, Chrysler or Ford.