The United States has rejected the International Maritime Organization’s (IMO) flagship Net-Zero Framework and threatened retaliatory measures against countries that back it. This decision risks undermining global efforts to establish a carbon pricing mechanism for shipping, which accounts for nearly 3% of global CO2 emissions.
In a joint statement released on 13 August, senior officials within the Trump administration, including Secretary of State Marco Rubio and Commerce Secretary Howard Lutnick, declared that the IMO’s framework represented ‘a global carbon tax on Americans levied by an unaccountable UN organisation.’ The statement added that Washington ‘will not tolerate any action that increases costs for our citizens, energy providers, shipping companies and their customers, or tourists.’
The IMO’s Net-Zero Framework, which was provisionally agreed by member states in April 2025, sets mandatory emissions reduction targets and introduces a pricing mechanism to accelerate the transition to low- and zero-carbon fuels. Central to the plan is a $100 per tonne levy on CO2 emitted above a defined threshold, with penalties of up to $380 per tonne for the least efficient ships. The scheme also establishes a carbon credit trading system that enables owners of more energy-efficient vessels to sell credits to operators of higher-emitting fleets.
If formally adopted in October, the Net-Zero Framework would apply to ships over 5,000 gross tonnes (GT) and require a 30% cut in emissions intensity by 2035 and 65% by 2040 against 2008 levels. The measures are scheduled to come into force in 2027 and will require support from two-thirds of IMO members that have ratified pollution-control conventions. To date, 63 countries including China, Brazil and the EU member states have indicated support, while the US walked out of talks in April.
The Trump administration argues that the framework disadvantages US shipping, in particular its LNG and biofuels sector. The joint statement said: ‘These fuel standards would conveniently benefit China by requiring the use of expensive fuels unavailable at global scale. These standards would also preclude the use of proven technologies that fuel global shipping fleets, including lower emissions options where U.S. industry leads such as liquified natural gas (LNG) and biofuels.’
The statement continued: ‘Our fellow IMO members should be on notice that we will look for their support against this action and not hesitate to retaliate or explore remedies for our citizens should this endeavor fail.’
The threats come against the backdrop of wider US disengagement from international climate cooperation. President Trump has already confirmed withdrawal from the Paris Agreement and has resisted commitments to curb plastic pollution.
Despite opposition from Washington, support among leading carriers for a global carbon levy is growing. Many shipowners have already set net-zero targets and see carbon pricing as essential to levelling the cost gap between conventional marine fuels and alternatives such as ammonia, methanol and green hydrogen. Environmental advocates describe the IMO plan as the most significant step yet towards aligning international shipping with global climate goals.
