ALBUQUERQUE, N.M. (AP) -- The U.S. Environmental Protection Agency has been notified by one of the nation's largest American Indian tribes that it intends to sue over the agency's lack of action on an air permit application for a proposed coal-fired power plant.

The Navajo Nation's Dine Power Authority and Houston-based Sithe Global Power have partnered to build the $3 billion Desert Rock plant, which would be capable of producing electricity for more than 1 million homes in cities across the Southwest.

Navajo Deputy Attorney General Harrison Tsosie told The Associated Press on Wednesday that the tribe and Sithe applied for an air permit in May 2004 but that the EPA has yet to make a ruling.

"Under federal law, the agency has a year to make a determination and issue a decision," Tsosie said. "It has been the practice that they take longer than a year, which is to be expected, but in the case of this particular application ... it has been almost four years."

Wendy Chavez, a spokeswoman with the EPA's regional office in San Francisco, said the agency has received the tribe's notice of intent to sue.

"There just hasn't been sufficient time to review it and comment on it," she said.

The 1,500-megawatt plant would be built on tribal land near the Navajo community of Burnham, southwest of Farmington. The area already is home to two other coal-fired plants.

Some Navajos and environmentalists argue that Desert Rock would harm the environment and residents' health. But DPA and Sithe have touted it as one of the cleanest coal-burning plants in the country and a much-needed source of jobs and revenue for the Navajo Nation.

The air permit would set limits for emissions covered under the federal Clean Air Act, such as sulfur dioxide, nitrogen oxides, carbon monoxide, particulates and lead emissions. Both federal officials and Desert Rock developers have said the draft permit contains some of the strictest controls ever set for a coal-fired power plant in the United States.

The New Mexico Environment Department and others have criticized the draft permit for not including enforceable conditions to address adverse visibility and for not analyzing mercury or carbon dioxide emissions.