State and local utility regulators will have to sign off on Entergy Corp.'s plan to turn over control of its power transmission system to an Indiana-based grid operator by the end of 2013.Entergy said Monday that it will file formal proposals by May 12 to join the Midwest Independent System Operator.

The system includes power companies, which cover all or most of South Dakota, North Dakota, Nebraska, Minnesota, Iowa, Wisconsin, Illinois, Indiana and Michigan and parts of Montana, Missouri, Kentucky and Ohio.

The federal government wants private power providers to form regional transmission organizations to allow the companies to buy and sell excess electricity. The system would allow Entergy for sharing resources among the four states where it has regulated power businesses — Louisiana, Mississippi, Arkansas and Texas.