The world shipping industry could accept a global levy on carbon emissions from merchant ships under a deal that would also channel proceeds to poor countries, according to an announcement at the UN climate talks on Tuesday.
Maritime transport accounts for roughly three percent of world emissions of greenhouse gases.
But, like the aviation industry, it does not have any targeted curbs on this pollution, an omission that green campaigners are fighting to change.
In a joint statement, the International Chamber of Shipping (ICS), WWF and Oxfam said carbon emissions from merchant ships could be subjected to "market-based measures" as an incentive to reduce greenhouse gases.
Part of the revenue from this could go to a planned Green Climate Fund that, in theory, will provide up to 100 billion dollars a year for developing countries most at risk from climate change.
WWF's director of international climate policy, Keya Chatterjee, said the deal was "an agreement in principle" and some details, including the carbon price, needed to be hammered out in further negotiations in the UN's specialised shipping organisation.
The ICS, which accounts for more than 80 percent of the world's merchant fleet, prefers a straightforward levy but the WWF could accept other options, she said.
Chatterjee described the accord as a breakthrough.
Failing to factor in the cost of fossil-fuel pollution from transport was "a subsidy... an enormous failure," she told AFP.
The announcement was made on the second day of talks in Durban under the 194-nation UN Framework Convention on Climate Change (UNFCCC).
ICS Secretary General Peter Hinchliffe said in the statement that the rules should be crafted under the UN's International Maritime Organization (IMO), "with the same rules for carbon reduction applying to all internationally trading ships, but in a manner which respects the principles of the UN climate convention.
"If governments decide that shipping should contribute to the UNFCCC 'Green Climate Fund'," said Hinchcliffe, "the industry can probably support this in principle as long as the details are agreed at the IMO, with the industry's clear preference for a market-based mechanism being a compensation fund linked to the fuel consumption of ships, rather than an emissions trading scheme."
Chatterjee said she hoped the UNFCCC talks, running until December 9, would set a date by which the IMO would craft the rulebook.
Explore further: Rolling lab tracks methane to its source