LONDON -- The head of the United Nations called Monday for maritime nations to agree on a course for the shipping industry to reduce its climate-harming emissions to net zero by the middle of the century at the latest.

       The appeal by U.N. Secretary-General Antonio Guterres came at the start of a meeting of the International Maritime Organization in London that's seen as key for helping achieve the international goal of limiting global warming to 1.5 degrees Celsius (2.7 Fahrenheit).

       “Shipping, which accounts for almost 3% of global emissions, will be vital,” Guterres said.

       He urged delegates to agree a new greenhouse gas strategy for shipping that includes “ambitious science-based targets starting in 2030 – both on absolute emissions reductions and the use of clean fuels.”

       The IMO's current target is for the shipping industry to cut its emissions by at least half from 2008 to 2050.

       Guterres said the new targets should include all greenhouse gas emissions caused by the industry and backed the idea of introducing a carbon price for shipping.

       Campaigners have suggested that funds generated from a levy on emissions could be used to help poor nations tackle climate change, though the industry wants the money to go toward the development of clean technologies.

       In May, The Associated Press revealed an influential shipping industry group was quietly warning shippers to think carefully before they sign up for an ambitious plan to reduce maritime emissions.

       The International Chamber of Shipping, which represents four fifths of the world’s commercial fleet, said member companies should “give careful consideration to the possible implications” before adopting stringent targets.