London (AFP) — An ambitious plan by the UN’s shipping agency to cut maritime emissions could be scuttled at the last minute after the United States threatened to impose sanctions on those supporting it.

Already approved in April, members of the London-based International Maritime Organization (IMO) are set to formally adopt the Net Zero Framework (NZF) on Friday as part of talks opening Tuesday.

The framework requires ships to progressively reduce their carbon emissions starting in 2028, and achieve complete decarbonization by 2050.

But the United States on Friday threatened sanctions and other punitive actions against those who support it, potentially derailing the plans.

Top US diplomat Marco Rubio, Energy Secretary Chris Wright and Transportation Secretary Sean Duffy said in a statement the administration of President Donald Trump “unequivocally rejects” the NZF proposal.

They threatened a range of punishing actions against countries that vote in favor of the framework, from visa restrictions to blocking vessels registered in those countries from US ports and imposing commercial penalties.

The NZF would require all ships to use a less carbon-intensive fuel mix or face financial penalties.

In April a majority of members — 63 states — voted in favor, including the European Union, Brazil, China, India and Japan.

Sixteen states voted against the measure, including major oil producers Saudi Arabia, Russia and the United Arab Emirates.

Pacific Island states abstained from the vote, deeming the proposals insufficient to meet decarbonization goals.

The United States had withdrawn from negotiations, not commenting on the proposal until last week.