The meeting of the seven leading industrialised nations in Turin is the first big political session since the world pledged at the UN's COP28 climate summit in December to transition away from coal, oil and gas.

Coal is the most polluting fossil fuel and environmentalists have urged the G7 -- which brings together Canada, France, Germany, Italy, Japan, the UK and US -- to lead the way on the pledge.

The latest G7 draft calls to "phase out existing unabated coal power generation in our energy systems during the first half of 2030s or in a timeline consistent with keeping a limit of 1.5°C temperature rise within reach, in line with countries' net zero pathways", according to a European source.

The two-day talks in the northern Italian city, home to Italy's automotive industry, are due to wind up with a final statement on Tuesday.

A fixed time frame would be hailed an important step.

Some, including France, have been calling for a phase out no later that 2030, but Japan in particular, which relies on coal for about a third of its electricity, has been unwilling to commit to any date.

Rome, which holds the G7 rotating presidency this year, has already pledged to turn off its coal-power plants by 2025, except on the island of Sardinia, which is expected to follow by 2028.

Together the G7 makes up around 38 percent of the global economy and was responsible for 21 percent of total greenhouse gas emissions in 2021, according to the Climate Analytics policy institute.

Countries agreed under the 2015 Paris Agreement to cap global warming at "well below" two degrees Celsius above average levels measured between 1850 and 1900 -- and 1.5C if possible.

Nearly 1.2C of global heating so far has already unleashed an escalating barrage of deadly impacts across the planet.

To keep the 1.5C limit in play the UN's climate expert panel have said emissions need to be slashed almost in half this decade.

But they continue to rise, driven largely by the burning of fossil fuels.

The UN's Environment Programme warned in November that countries' existing carbon-cutting plans put the world on a path for heating of between 2.5C and 2.9C by 2100, risking catastrophic consequences for humanity and irreversible tipping points on land and in the oceans.