Sen. Kevin Cramer of North Dakota is leading a group of nine Republican senators warning fellow Republican Chuck Grassley, the chairman of the Finance Committee, not to allow for the extension of wind tax credits set to expire at the end of the year.

The senators, most from major fossil fuel-producing states, say wind has become cost competitive with other energy sources and does not need federal subsidies anymore. Grassley, an Iowa senator, is a leading champion of the wind industry. His state had the second-most installed capacity of wind as of April. Iowa generates 42% of its electricity from wind.