In a sweeping effort to reduce its environmental impact, New York City is planning to overhaul the energy-efficiency standards of all its public buildings and to pressure private landlords to make similar improvements.

The initiative is part of a pledge, to be announced before the start of the United Nations Climate Summit on Tuesday, to decrease greenhouse gas emissions by 80 percent by 2050 from 2005 levels. The United Nations has pointed to that rate of decrease as a desired target for developed countries to mitigate the effects of climate change.

New York would become the largest city in the world to make the commitment, according to the city’s leaders.

Though the proposal is likely to rankle some residential and commercial building owners, who will bear a portion of its cost, officials have framed the issue in part as an extension of the citywide focus on income inequality since Mayor Bill de Blasio took office in January. High energy costs, the de Blasio administration argues, amount to a regressive tax, because lower-income residents by and large pay a higher share of their rent for energy than wealthier residents, and often live in less-efficient buildings. The long-term savings could prove to be a financial boost for lower-income residents, officials said — to say nothing of the environmental benefits.