The Environmental Protection Agency (EPA) on Wednesday announced it was proposing the first U.S. emissions standards for commercial aircraft.

In 2016, the U.N. International Civil Aviation Organization (ICAO) agreed on global airplane emissions standards aimed at makers of small and large planes, including Airbus SE and Boeing Co., which both backed the standards.

The EPA-proposed regulation seeks to align the United States with the ICAO standards, EPA Administrator Andrew Wheeler said. "We are implementing the ICAO recommendations, ICAO standards," Wheeler told reporters.

Reuters, which first reported the proposal earlier Wednesday, would apply to new type designs as of January 2020 and to in-production airplanes or those with amended type certificates starting in 2028. They would not apply to airplanes currently in use.

Aircraft account for 12% of all U.S. transportation greenhouse gas emissions and 3% of total such U.S. emissions. They are the largest source of transportation-related greenhouse gas emissions not subject to standards.

Wheeler said it was critical the U.S. adopt the standards, because countries could ban U.S.-assembled airplanes if they do not meet ICAO standards.

EPA is expected to finalize the rules next spring. The Federal Aviation Administration will then issue separate rules to enforce the standards.

Some environmentalists argue the ICAO rules and EPA did not go far enough.

Clare Lakewood, climate legal director at the Center for Biological Diversity, said Wednesday, "this toothless proposal does nothing to meaningfully address the serious problem of airplanes’ planet-warming pollution." She noted EPA was not estimating any emissions reductions as a result of the proposal.

Wheeler said the proposal is based on "where the technology is today ... You can't really set the standard that can't be met."

Boeing said the EPA proposal "is a major step forward for protecting the environment and supporting sustainable growth of commercial aviation and the United States economy."

Airlines for America, a trade group, said the rules will help U.S. airlines "achieve carbon neutral growth in the near term and to cut net carbon emissions in half in 2050 relative to 2005 levels."

Under President Barack Obama, the EPA in 2016 declared aircraft emissions posed a public health danger. In January, environmental groups filed a notice of intent to sue EPA for failing to regulate aircraft emissions.