American Samoa has joined 11 states and three cities in the United States which are suing the federal government's Environmental Protection Agency.
The plaintiffs allege the EPA has failed to regulate greenhouse gas pollutants.
The legal challenge is an effort to compel President Bush's adminstration to take the effects of global warming into account when shaping emissions laws.
Attorneys General from the 11 states first raised concerns about global warming in a July 2002 letter to the Bush Administration.
They cited a federal report that confirmed the dangers of global warming and urged President Bush to act immediately and take a "strong national approach" to the problem.