WASHINGTON — The Environmental Protection Agency moved Wednesday to start the process of regulating greenhouse gas emissions from the nation’s fleet of commercial aircraft, a long-desired objective of environmental groups. But some fear the ultimate approach may prove too weak.

The agency released a proposed “endangerment finding,” meaning that it is suggesting that aircraft engines may “contribute to the air pollution that causes climate change and endangers public health and welfare.” That’s what the EPA has found for emissions from an even larger contributor to global warming: cars.

The EPA also gave notice that it is considering regulations on aircraft engines. But rather than moving ahead on its own, the agency plans to continue to work with the United Nations’ International Civil Aviation Organization, which is expected to create its own global rules in early 2016. The EPA called Wednesday’s announcement “an initial step in the process for EPA to adopt CO2 standards promulgated by ICAO in the future.”

What has some environmental groups worried is this apparent deferral to a global international body. “Passing the buck to an international organization that’s virtually run by the airline industry won’t protect our planet from these rapidly growing emissions,” Vera Pardee, attorney for the Center for Biological Diversity, said.

According to the EPA, commercial aircraft contribute 11 percent of emissions from the U.S. transportation sector, and overall, 3 percent of U.S. emissions. That may sound relatively small, and in comparison to cars or power plants, it is.

But car emissions are already regulated, and power plant emissions would be soon under the proposed Clean Power Plan.