It’s rare for an industry powered by fossil fuels to call for a tax on its own carbon emissions. Yet the shipping sector is doing just that.

Several trade groups, representing more than 90% of the world’s merchant fleet, have submitted a proposal to shipping’s United Nations regulator calling for it to prioritize a carbon tax for the industry, the International Chamber of Shipping said Wednesday. While it’s unlikely any levy will be imposed immediately, the call highlights the growing pressure shipping is under to decarbonize from customers and politicians alike.

The International Maritime Organization approved new emissions rules in November, but the trade groups say these won’t be enough to hit the UN body’s 2050 climate targets — which include a halving of annual greenhouse gas emissions versus 2008 levels. Instead, talks on a market-based-measure that would put a price on pollution should start “as soon as possible and before 2023,” the groups say.

The industry isn’t the first to call for such a tax. Commodity trading giant Trafigura Group has suggested a levy of $250 to $300 a ton of carbon dioxide on ship fuels, while the Marshall Islands and Solomon Islands have proposed a duty on greenhouse gases from international shipping. Meanwhile, the European Union is considering whether to include shipping — at least within the bloc — in its Emissions Trading Scheme.