The United States has threatened trade and diplomatic retaliation against nations that support a new U.N. plan to curb shipping emissions, warning that tariffs, visa restrictions, and port levies could follow if the deal advances.

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At the center of the dispute is the International Maritime Organization’s (IMO) draft “Net-Zero Framework,” which proposes fees on ships that exceed carbon emissions limits. The agreement, struck in April, is set for a decisive vote at the IMO’s extraordinary session in October.

Washington withdrew from negotiations earlier this year and has since warned that backing the framework would unfairly burden global shipping while offering little real progress on climate goals. A U.S. State Department spokesperson confirmed the administration is “actively exploring and preparing to act on remedies including tariffs, visa restrictions, and/or port levies” if the deal is adopted, adding that the U.S. is urging its partners to take similar measures.

Several governments, including the Netherlands, have received direct warnings. A Dutch infrastructure ministry spokesperson confirmed that U.S. representatives cautioned the country could face tariffs or other penalties if it supported the plan. It remains unclear how many other IMO members have been approached.

The IMO, which regulates global shipping safety and emissions across its 176 member states, stressed that the October session will allow concerns to be addressed ahead of any vote. Global shipping currently generates nearly 3% of worldwide CO2 emissions, with about 90% of global trade moving by sea. Supporters of the framework argue that without decisive measures, emissions will rise sharply.

The initial April draft passed with 63 votes in favor, 16 against, and 24 abstentions. With a majority needed, the outcome of the October vote is uncertain—especially amid mounting U.S. pressure on allies.