Nearly 200 shipping companies have urged maritime nations to support the first-ever global fee on greenhouse gas emissions, reports the Associated Press.

Populists worldwide, led by the America's Trump administration, see this corporate unanimity as a way of increase environmental compliance costs beyond reach of smaller shipping companies, as well as contending that such measures will have little or no impact on climate mitigation.

The Getting to Zero Coalition, comprising companies, governments and intergovernmental bodies, is calling on International Maritime Organisation member states to adopt the fee and related green shipping regulations at next month's meeting in London.

Jesse Fahnestock of the Global Maritime Forum, which manages the coalition, said industry voices must be heard given the significance of the decision.

The Trump administration opposes the proposal, calling it a "global carbon tax on Americans" and threatening retaliatory measures such as tariffs, visa restrictions and port levies.

Despite government opposition, US-based shipping firms support the plan. The Chamber of Shipping of America favours a single global system to avoid overlapping regional charges.

Shipping emissions now account for about three per cent of global totals. The IMO aims for net-zero emissions by 2050 and wider use of low-emission fuels.

In April, IMO members agreed to a framework imposing a minimum fee per tonne of emissions and a marine fuel standard. The United States did not participate in the vote but will send a delegation to the October meeting.

If approved, the regulations will take effect in 2027 and apply to ships over 5,000 gross tonnes, which produce 85 per cent of international shipping emissions.

Environmental groups warn that failure to adopt the rules will delay decarbonisation and hinder efforts to limit global warming.

While US officials argue the standards are unattainable and favour China, most countries appear to support the regulations, said Faig Abbasov of Transport and Environment.

Shipping firms say the rules offer investment certainty for cleaner technologies. The International Chamber of Shipping, representing over 80 per cent of the global fleet, is also backing adoption.