The agency may issue carbon pollution reduction mandates for vehicles as early as next month, and then would move to implement ones for fixed sources such as cement kilns, coal-fired power plants and oil refineries.

The senators are Mark Begich, Alaska; Carl Levin, Michigan; Claire McCaskill, Missouri; Max Baucus, Montana; Sherrod Brown, Ohio; Robert Casey, Pennsylvania, and Robert Byrd and Jay Rockefeller of West Virginia.

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