The Obama administration is leaning toward revising its landmark proposal to regulate greenhouse gas emissions from new power plants, according to several individuals briefed on the matter, a move that would delay tougher restrictions and anger many environmentalists.

The discussions center on the first greenhouse gas limits for power plants, which were proposed by the Environmental Protection Agency nearly a year ago. Rewriting the proposal would significantly postpone any action and also might allow the agency to set more permissive standards for coal-fired power plants, which are roughly twice as polluting as those fueled by natural gas.