New York is among the states and environmental groups that reached a late 2010 settlement with EPA in which the agency committed to setting rules for new and existing plants.

The 11 other parties signing the notice include the states of Connecticut, Vermont, Oregon, Delaware, Maine, Massachusetts, and the cities of New York and the District of Columbia.

In addition to missing the deadline for rules for existing plants, EPA has also not moved ahead with emissions guidelines for existing power plants, which are on a slower track.

Green groups sent a separate notice to EPA this week that similarly threatened litigation to force EPA’s hand.

“This 60-day notice is required under the Clean Air Act before an enforcement lawsuit may be filed, and we hope EPA will use this time to complete its work on these critical standards,” said David Doniger, a senior attorney with the Natural Resources Defense Council.

“EPA must then promptly issue carbon pollution standards for existing power plants as the Clean Air Act also requires,” he said.