WASHINGTON (Reuters) - Three environmental groups filed a lawsuit against the Environmental Protection Agency on Tuesday to press for faster action in setting limits on greenhouse gas emissions from U.S. aircraft.

A passenger plane approaches to land as other aircraft taxi to the runway at the San Diego International Airport in San Diego, California, April 22, 2013. REUTERS/Mike Blake

Earthjustice, the Center for Biological Diversity and Friends of the Earth filed the lawsuit to force the agency to complete its “endangerment finding,” a step in the EPA rule-making process that would allow the agency to regulate carbon dioxide emissions from U.S. aircraft.

Any “unreasonable delay” in setting emission standards for aircraft violates the law and the EPA’s duty under the Clean Air Act, according to the lawsuit filed in U.S. District Court for the District of Columbia.

Carbon dioxide emissions raise average temperatures, contributing to climate change. U.S. aircraft account for 3 percent of U.S. total CO2 emissions. There currently are no restrictions on greenhouse gas emission from aircraft.

The United States accounts for half of worldwide CO2 emissions from aircraft. Emissions from the aviation sector are projected to triple by 2050 without regulations.

The EPA was expected to finalize a proposal for an endangerment finding in mid-2014. But last June it issued only a preliminary scientific finding on the emissions.

The environmental groups want the agency to publish its final finding, opening it up to a public comment period, before President Barack Obama leaves office.

The agency has said it plans to implement a global carbon dioxide emissions standard being developed by the United Nations’ International Civil Aviation Organization.

The EPA is expected to finalize the endangerment finding this summer, spokeswoman Laura Allen said. The agency would then undertake a rule-making process to adopt standards “at least as stringent as the ICAO standards” and formally propose them in 2017, she said.

“The standards he (Obama) is prepared to accept for carbon pollution from airplanes are embarrassingly low,” said Sarah Burt, a legal expert on aviation for Earthjustice.

The standards expected to be adopted by the ICAO later this year are aimed at makers of small and large planes alike and would apply to all new aircraft models launched after 2020.

Environmental groups have argued that the standards would make barely a dent in emissions from the aviation sector, one of the fastest-growing carbon emissions sources.

“We have to push them to issue a final (endangerment finding) and CO2 standard so we can have a conversation about what the standard should be,” said Marcie Keever, legal director for Friends of the Earth. “We wish the EPA wasn’t defaulting and deferring to ICAO and instead would lead the way,” she said.