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Charlie Neibergall, Associated Press
Democratic presidential candidate Hillary Rodham Clinton speaks during a house party, Sunday, July 26, 2015, in Carroll, Iowa.

DES MOINES, Iowa — Hillary Rodham Clinton is detailing new energy proposals in Iowa to address climate change. She calls global warming one of the "most urgent threats of our time."

But she's still not taking a position on the Keystone XL oil pipeline.

The Democratic presidential contender is proposing that every home in the United States be powered by renewable sources by 2027. Her plan calls for installation of 500 million solar panels over four years.

Clinton laid out clean-energy ideas during a tour of a regional bus station in Des Moines, Iowa, on Monday.

When asked about the Keystone XL oil pipeline opposed by environmental activists, she would not comment except to say she wants a State Department review of the project to run its course.