The United States has formally opposed the UN's International Maritime Organisation's proposed "Net-Zero Framework," calling it a global carbon tax and threatening retaliation, reports Saint Petersburg's PortNews.

In a joint statement issued on 12 August, Secretaries Marco Rubio, Howard Lutnick, Chris Wright and Sean Duffy said the framework would unfairly burden the US and harm its economic interests.

The statement, released by the Office of the Spokesperson, said President Trump "will not accept any international environmental agreement" that disadvantages Americans.

The proposal was described as benefiting China and penalising US shipping by mandating expensive fuels not widely available, while excluding LNG and biofuels.

Officials warned that vessels failing to meet fuel and emissions standards would face steep fees, raising costs for energy, transport and leisure cruises.

Even small ships could incur millions in penalties, the statement claimed, with direct impacts on American consumers.

The administration said it "unequivocally rejects" the framework and "will fight hard" to defend US citizens, energy providers, shipping firms and tourists.

It also warned fellow IMO members that the US would seek support to block the proposal and "not hesitate to retaliate or explore remedies" if necessary.

The IMO's "Net-Zero Framework" is scheduled for consideration in October and aims to accelerate decarbonisation across global shipping.