Hundreds of people have signed up to tell the Environmental Protection Agency what they think of proposed rules to cut pollution from power plants during public hearings in Denver.
Opponents and supporters will also stage rallies and news conferences around the city during the hearings on Tuesday and Wednesday.
The EPA is holding hearings this week in Denver, Atlanta, Pittsburgh and Washington, D.C., on President Barack Obama's plan to cut carbon dioxide emissions by 30 percent by the year 2030.
The rules are intended to reduce greenhouse gases and restrain global warming.
Representatives from coal mines, electric utilities, labor unions, environmental groups, renewable energy companies, government agencies and religious and civil rights organizations are among the 400 people who plan to speak in Denver.