The U.S. abandoned global talks aimed at cutting shipping’s carbon emissions and threatened to reciprocate against any fees that the country’s merchant fleet incurs if such an initiative proceeds.

The UN’s shipping agency, the International Maritime Organization, is meeting in London April 7-11 with a goal of agreeing some sort of carbon charge for the maritime sector. The U.S. stance was conveyed in a message to other governments that was seen by Bloomberg and confirmed as genuine by delegates from two other countries.

It’s unclear where this will leave attempts to decarbonize shipping. Speaking before this week’s meeting, there was optimism among several people following the talks that the U.S. couldn’t unilaterally upend the process. There’s a wider question now about whether other countries will follow Washington’s lead.

“The U.S. rejects any and all efforts to impose economic measures against its ships based on greenhouse gas emissions or fuel choice,” according to the communication. The U.S. “urges your government to reconsider its support for the GHG emissions measures under consideration.”

While the U.S. is economically and diplomatically powerful, the country’s fleet of commercial ships is relatively small. That’s important because so-called flag-states — the places where vessels are registered — are integral to implementing the IMO’s air-pollution rules.

The IMO’s Marine Environment Protection Committee, the body that would approve the carbon-reduction measures, normally makes decisions by consensus. While a ballot is a possibility, the U.S.’s vote wouldn’t carry more weight than that of other nations, but it might be able to influence others into voting in a certain way. 

“There are no indications from within the room that the U.S. statement has had a significant impact,” said Jesse Fahnestock, director of decarbonization at the Global Maritime Forum, a nonprofit with partners including BP Plc, on April 8. “The talks very much seem to be proceeding as they were yesterday.”

The GHG-cutting regulations being discussed this week would be amendments to MARPOL Annex VI, the main international treaty on preventing air pollution from ships. 

While the U.S. has ratified that annex, a country can withdraw from the full convention, or any of the optional annexes, according to Tore Longva, decarbonization director at ship classification society DNV.

“Our government will consider reciprocal measures so as to offset any fees charged to U.S. ships and compensate the American people for any other economic harm from any adopted GHG emissions measures,” the message said. 

Back in 2023, the IMO set targets for cutting ships’ greenhouse gas emissions, including getting the sector to net zero by mid-century.

“We’re working on a compromise proposal,” the Secretary General of the IMO, Arsenio Dominguez, told journalists on Monday. “There will be a price on emissions.”

An email sent late April 8 to the U.S. State Department wasn’t immediately answered.