"It's all about politics. We've met all of the requirements, done all of the work, and yet we're still waiting," said Christopher Deschene, an attorney for the Dine Power Authority, the tribe's partner in the project. "This is our back yard. We can handle this."

The EPA says it was initially delayed by climate-modeling uncertainties for a region that includes several national parks, and then by nearly 1,000 mostly negative comments posted on the agency's Web site. Air-permit technicians say they have a duty to answer each of the comments.

Added to the debate is a recent analysis of government temperature data that shows the interior American West is heating up at twice the global rate.

"We think we're doing our job as best we can — the good technical work that we are required to do," said Colleen McKaughan, a Southwest region deputy air-division director for the EPA. She declined to provide a timeline for action.

Environmental groups have vowed to keep fighting any EPA permit.

"There is no such thing as clean coal," said Theodore Spencer, a climate policy analyst for the Natural Resources Defense Council. "Coal power is pretty much the dirtiest power there is, and that plant would do nothing to address global-warming emissions."