(Bloomberg) -- Group of 20 ministers are likely to end talks this week without an ambitious deal on climate change, another setback in the fight against rising temperatures ahead of key negotiations this year.

Energy and environment ministers at a G-20 meeting in Naples, Italy, are stuck on a number of issues, according to several officials and diplomats familiar with the discussions. They will kick a final decision to a meeting of their leaders in October.

The parties haven’t been able to agree on specific actions and firm timetables needed to reach net-zero global emissions by 2050 and keep global warming at 1.5 degrees Celsius, according to a draft communique and the officials.

Despite major net-zero commitments from the world’s largest polluters in the past 12 months -- and a backdrop of dramatic weather events -- two people familiar with the talks said it would be extremely difficult to reach a substantive agreement given the scale of the differences. Securing an ambitious plan is one the main goals of the G-20 this year, ahead of international climate talks in Glasgow in November.

For a second time this month, G-20 ministers will once again fail to agree on net zero greenhouse gas emissions or keeping global warming to 1.5 degrees Celsius - the lower end of the goal agreed in Paris in 2015. Instead the ministers only recognized “the impacts of climate change at 1.5°C are much lower than at 2°C”.

Phasing out coal, the dirtiest fossil fuel, is one sticking point, as G-20 chair Italy is pushing for a phase-out to be included in the communique for the first time. But the draft document shows the group won’t commit to ending the use of coal domestically, and only urges its members to follow the G-7 in ending overseas coal finance.

Two developed economies are pushing back against new commitments on coal, and a handful of emerging economies are also resisting an effort to define clearer targets, the people added. The draft communique instead focuses on “deployment and dissemination of high efficient technologies” to end the use of “unabated coal.”

Key Climate Talks Are Headed for Trouble After G-7 Wrangling

Both the G-7 and the G-20 are seen as staging posts along the path to the global climate talks known as COP26, due to be held in Glasgow in November. G-20 leaders are set to meet in Rome right before that gathering.

Last month’s summit of G-7 leaders in England highlighted the difficulty of reaching agreement on climate at the highest levels of power. Those countries agreed to stop funding coal overseas but failed to halt its domestic use. Progress was blocked by last-minute nerves, political tensions and a shortfall of funding.

With just 100 days until the start of COP26, time is running out, said John Kerry, the U.S. special presidential envoy for climate, during a speech in London this week. The talks come as countries around the world are feeling the effects of climate change, with nations from China to Germany suffering intense flooding and heat waves.

Kerry has said the COP26 is the last chance to keep alive the chance of limiting temperature rise to 1.5 degrees Celsius. On Wednesday, he said that at the very least, he expects the G-20 meeting to agree to keep warming to “well below” 2 degrees Celsius, striving for 1.5 degrees Celsius -- the language agreed to in Paris in 2015.

“My hope is that we’ll find a pretty easy agreement on the major goals because we broke that ground in Paris,” he said in an interview. “But we need to raise ambition now.”

The U.S. remains well short of financial commitments to support energy transitions in developing countries -- though Kerry has said more money will be delivered.

(Updates throughout with details of draft communique)

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