An aging nuclear power plant just north of New York City will close by April 2021 under a deal between New York State and plant owner Entergy Corp., Gov. Andrew Cuomo said Monday.

Cuomo has long argued the two-unit Indian Point plant, about 50 km north of Manhattan, should be shuttered to protect the millions of people living nearby.

"For 15 years, I have been deeply concerned by the continuing safety violations at Indian Point, especially given its location in the largest and most densely populated metropolitan region in the country," he said in a statement.

The plant's two reactors went online in 1974 and 1976, respectively. Under the deal, one of them will be shut down by April 2020 and the other by April 2021.

Operational problems, including faulty bolts and various leaks and fires, have called into question the safety of operating Indian Point over the years. There are also external threats such as an underlying earthquake fault.