WASHINGTON — An ambitious UN plan to cut emissions from global shipping faces uncertainty after the United States threatened sanctions against countries supporting the proposal.

The International Maritime Organization (IMO), the London-based UN agency for shipping, approved the Net Zero Framework (NZF) in April. Members are set to formally adopt the framework on Friday, following talks that began Tuesday. The NZF requires ships to progressively reduce carbon emissions starting in 2028 and achieve full decarbonization by 2050.

However, U.S. officials last week warned of punitive measures, potentially derailing the agreement. Top diplomats—including Senator Marco Rubio, Energy Secretary Chris Wright, and Transportation Secretary Sean Duffy—stated that the Trump administration “unequivocally rejects” the NZF. They threatened actions ranging from visa restrictions to barring vessels from U.S. ports and imposing commercial penalties on countries that support the framework.

The NZF would require ships to use a lower-carbon fuel mix or face financial penalties. In April, 63 member states—including the European Union, Brazil, China, India, and Japan—voted in favor. Sixteen countries, including major oil producers Saudi Arabia, Russia, and the UAE, voted against it. Pacific Island nations abstained, citing insufficient ambition.

The U.S. had largely stayed out of negotiations until last week. European officials reaffirmed full support for the proposal, but a European source told AFP that the U.S. threats could influence “countries more sensitive to U.S. pressure and vulnerable to retaliation.”

Consensus, typically the norm in IMO decisions, has already been ruled out. Countries like the Philippines, home to the world’s largest maritime workforce, could be particularly affected by visa restrictions. Caribbean nations dependent on U.S. cruise tourism also face potential sanctions.

IMO Secretary-General Arsenio Dominguez declined to respond directly to the U.S. statement but said he remains “very confident” in the NZF vote.

The framework includes an emissions tax for ships exceeding set limits, creating a fund to reward low-emission vessels and support climate-vulnerable countries. If adopted, the global system would be difficult to evade—even for the United States—thanks to IMO rules allowing inspections and detention of non-compliant ships.

Since returning to power in January, Trump has reversed U.S. climate policies, calling climate change a “scam” and promoting fossil fuel use through deregulation.