The pledge still allows for some "limited" exceptions of fossil-fuel financing so long as they are consistent with the 2015 Paris pact to curb global temperature increases.
Japan for the first time joined fellow members of the Group of Seven industrialised nations in pledging to end public financing for fossil fuel projects abroad by the end of the year to help combat global warming.
"We commit to end new direct public support for the international unabated fossil fuel energy sector by the end of 2022," G7 energy and climate ministers said in a joint statement following talks in Berlin on Friday.
The term "unabated" refers to projects that do not employ techniques to offset some of the pollution caused by carbon dioxide emissions.
Ending subsidies for the international fossil fuel energy sector was already part of a series of commitments agreed to by around 20 countries at last year's COP26 climate summit in Glasgow.
Six of the G7 club of rich nations were among the signatories at the time Britain, Canada, Germany, France, Italy and the United States – but Japan had resisted until now.
"It is good that Japan, the world's largest financier of fossil fuels, has now joined the other G7 countries in making a shared commitment to end overseas fossil fuel financing," said Alden Meyer, senior associate at climate policy think tank E3G.
Friday's pledge still allows for some "limited" exceptions of fossil-fuel financing so long as they are consistent with the 2015 Paris pact to curb global temperature increases. But Meyer said countries wishing to do so would face "a very stiff bar to clear".
At their G7 talks, ministers also committed to largely end the use of fossil fuels in their electricity sectors by 2035, despite heavy tensions in the power market over Russia's invasion of Ukraine.
"We further commit to a goal of achieving predominantly decarbonised electricity sectors by 2035," they said.
Clean energy transition
To achieve this, member states promised to ramp up "the necessary technologies and policies for the clean energy transition" and accelerate the phase-out of coal.
The pledge was welcomed by environmental campaigners, at a time when the war in Ukraine has sent energy prices soaring and Western countries are scrambling to wean themselves off Russian imports.
"In a very difficult geopolitical situation, the G7 are united behind an end to fossil fuels by 2035 in the power sector. This is significant progress," said David Ryfisch of the Germanwatch environmental group.
Speaking at the closing press conference, German Energy Minister Robert Habeck welcomed the pledges made by G7 nations, saying they sent a "strong signal for more climate protection".
As well as a pledge to stop bankrolling fossil fuel projects abroad by the end of the year, Habeck highlighted the club's agreement to ditch all "inefficient fossil fuel subsidies" by 2025.