MONTREAL/CANCUN (Reuters) - U.S. airlines on Tuesday affirmed their support for a plan to curb emissions from flights, under review by the administration of President Donald Trump who recently decided to take the country out of Paris climate change accord.

Several U.S. airlines and industry groups said they back the global aviation agreement approved by 70 countries, including the United States, to curb greenhouse gases from international flights.

Trump said on Thursday the United States would withdraw from the landmark 2015 Paris pact to fight climate change, raising questions about whether he would also seek to back out of the 2021 voluntary phase of the airlines agreement.

Air Transport Action Group told reporters at an industry gathering in Cancun, Mexico, on Tuesday that the deal was less costly for carriers than navigating around multiple regional or national rules.

Airlines for America, the trade group for major U.S. carriers, said in response to queries from Reuters that it remained committed to the agreement brokered by the International Civil Aviation Organization (ICAO).

At the Mexico event this week, the International Air Transport Association (IATA) and carriers like American Airlines AAL.O and United Airlines UAL.N reiterated their support for the deal.

A U.S. State Department spokeswoman said in an email that the aviation agreement was under review, as were all regulatory policies agreed by the Obama administration. There is no deadline for action, she said.

Under the global deal, airlines will buy carbon credits from environmental projects around the world to offset growth in emissions from international commercial flights.

The deal, known as the Carbon Offset and Reduction Scheme for International Aviation, has a voluntary phase starting in 2021 and that would become mandatory. Without the pact, airlines would be charged for emissions by regions like Europe.

“We believe having a series of national or regional measures overlapping and contradicting each other increases costs, administration, complexity,” said Michael Gill, executive director of the Air Transport Action Group.

“Having a single global approach brings significant financial and operational benefits,” he told reporters in Cancun.

Citing ICAO figures, he said the industry estimates the deal will cost airlines to $1.5 billion to $6.2 billion in 2025, depending on future carbon prices, and no more than 1.8 percent of industry revenues by 2035.

According to ICAO, airlines from 70 States, which account for almost 88 percent of international flights, will be covered by the deal.

Russia and India have said they would not participate in the voluntary phase from 2021 to 2026.