The UN’s net-zero push is coming to a head with the Trump administration efforts to revamp US shipping.

A fight is brewing ahead of the upcoming meeting of the International Maritime Organization (IMO) over new rules to reduce greenhouse gas emissions in the shipping industry. Formal approval at the October 14-17 meeting was assumed until the United States announced its opposition to the regulations in August and called on other governments to reject the proposal or face retaliation.

The IMO is an unlikely place for this confrontation. As a United Nations specialized agency focusing on setting universal standards for maritime safety and security, the IMO is rarely controversial. In fact, the IMO is one of only a handful of UN organizations identified in the Trump administration’s fiscal year 2026 budget request as deserving of US funding. Specifically, it was highlighted for its standards setting, efforts to reduce pollution and prevent maritime disasters, and enhancing US security by helping “secure shipping lanes against terrorism and related threats.”

Nonetheless, the IMO finds itself in the crosshairs of the Trump administration.

The dispute centers on draft amendments to the existing International Convention for the Prevention of Pollution from Ships (MARPOL), which the United States ratified in 1980 to address pollution of the marine environment by ships. The new rules, if approved in October, would be added to Annex VI of MARPOL and would apply to all parties to the agreement and annex 16 months after adoption through a process called “tacit acceptance.” The United States is a party to both MARPOL and Annex VI of the convention. 

These regulations seek to implement the IMO “Net-Zero Framework” through mandatory fuel standards for ships over 5,000 gross tonnage and financial penalties for those failing to comply. Military and domestic shipping vessels are exempted. Overall, however, covered ships account for about 85 percent of global emissions from the shipping industry.

Under the proposal, ships must reduce their annual greenhouse gas fuel intensity (the amount of greenhouse gas emitted for each unit of energy used). Specifically, ships with emissions over two specified thresholds, which increase annually from 2028 to 2035, would be required to pay fines ($100 per ton of excess emissions over the first threshold and $380 per ton of excess emissions over the second) into an “IMO Net-Zero Fund.” Revenues would be used to reward ships with low emissions, support research and technology transfer, and help mitigate the impact of the regulations on vulnerable states.

What impact will the new regulations have? The most recent IMO study found that shipping accounted for 2.89 percent of global anthropogenic emissions. The IMO projects that the regulations could reduce greenhouse gas emissions from shipping by 40 percent. Thus, if everything works as planned, the regulations will reduce global greenhouse gas emissions by about 1 percent.

But things may not go as planned. 

The new regulations would take effect in 2027, giving ships a relatively short window to come into compliance. According to shipping firms, fines could amount to “about $20 billion to $30 billion a year by 2030,” with the cumulative total possibly exceeding “$300 billion by 2035 if the global fleet misses targets by as little as 10%.”

The financial penalties are intended to incentivize compliance. However, the costs of compliance are even steeper. Over 90 percent of the current global fleet uses conventional fuels and cannot utilize greener alternatives. Retrofitting existing ships is expensive, and some may choose to pay the fines instead.

In addition to retrofitting ships, infrastructure also needs to be overhauled, including investments related to new alternative green fuel production and refitting ports for storage and bunkering. According to one estimate, “To meet the International Maritime Organization (IMO) 2050 emission targets, the scale of investment is estimated to be up to $1.9tn.”

Finally, there is the fact that alternative green fuels cost far more—at least three to four times more—than traditional fuels. Consequently, fuel costs are projected to rise by 350 percent. 

Overall, whether shippers comply or simply pay fines, the cost of shipping is likely to increase if the IMO regulations are implemented, and consumers will bear the brunt of the price.

The United States is opposed to these measures, which it sees as “effectively a global carbon tax on Americans levied by an unaccountable UN organization” to meet “unattainable fuel standards and emissions targets” that will drive up costs. The United States is also concerned that the rules would phase out proven technologies like liquified natural gas and biofuels in favor of alternative fuels, including ammonia and methanol, where China has an advantage. 

The United States warned that it “will not tolerate any action that increases costs for our citizens, energy providers, shipping companies and their customers, or tourists…and [will] not hesitate to retaliate or explore remedies” should the IMO adopt these rules. It subsequently clarified that these remedies could include “tariffs, visa restrictions, and port levies.”

Will the IMO adopt the new regulations despite US pressure? The draft was easily approved by a vote of 63 to 16 with 24 abstentions at a meeting of the IMO’s Marine Environment Protection Committee this past April. But 63 nations are only a third of all 176 IMO member states. In the upcoming October vote, there could be enough opposition to block the regulations or convince governments to consider changes.

This is not a situation where the United States can simply vote “no” and walk away.

US vessels are subject to inspection for compliance with MARPOL in foreign ports. Amendments to Annex VI, where these new regulations would be inserted, would similarly apply. Thus, the United States will be affected even if it votes against the new regulations. Hence, the threat of retaliation. If the other governments approve the new IMO regulations, they could invite reciprocal fees or inspections on foreign ships at US ports.

In addition, through its ratification of MARPOL and a subsequent Memorandum of Understanding, which “provides that EPA and USCG will jointly and cooperatively enforce the provisions of Annex VI,” the United States likely will have obligations to comply with the new regulations even if it opposes them. Depending on the level of US opposition, it may decide to withdraw from MARPOL or Annex VI, which would take effect 12 months after a notice of denunciation is communicated to the IMO Secretary-General. This could undermine existing IMO standards more broadly.

Relatedly, the European Union has enacted fuel and emissions standards similar to those under consideration at the IMO. Now that the United States has staked its position, if the EU enforces those regulations on US ships, it could trigger a response like that threatened if the new IMO regulations are adopted.

Other nations need to take the US opposition to the proposed IMO regulations seriously. The administration has demonstrated that it is willing to be disruptive and impose the trade measures it threatens. An off-ramp or alternative to address US concerns while preserving preexisting rules and relationships is the prudent course.