Environmental Protection Agency Administrator Gina McCarthy on Monday attempted to assuage fears about a forthcoming carbon emissions rule for existing power plants, as she said it would contain flexibility for states.

“The only thing I really hope when this proposal goes out is that people look at it and say ‘EPA listened,’ ” said McCarthy, speaking at a Washington event hosted by the Bipartisan Policy Center. The agency sent the proposed rule to the White House Office of Management and Budget last week for review.