Denmark should ban coal use by 2025 to make the Nordic nation a leader in fighting global warming, adding to green measures ranging from wind energy to bicycle power, Denmark's climate minister said on Saturday.

Denmark has already taken big steps to break reliance on high-polluting coal. Wind turbines are set to generate more than half of all electricity by 2020, and 41 percent of people in Copenhagen cycle to work or school.

"The cost (of phasing out coal) would not be significant," Climate, Energy and Building Minister Helveg Petersen said of a proposal he made this past week to bring forward a planned phase-out of all coal use to 2025 from 2030.

His ministry is studying details of how it would work before unveiling a formal plan.

Denmark imports about 6 million tons a year of coal on world markets, currently from Russia, so a ban would coincidentally cut dependence on Moscow for energy.

Denmark often gets high marks for its work to cut greenhouse gas emissions, which fell 25 percent from 1990 to 2012, among the steepest falls of any EU nation. It is aiming for a 40 percent cut from 1990 by 2020, matching the EU's goal for 2030.