ROME -- The Group of 20 major economies agreed to end financing of new unabated coal power generation abroad by the end of this year, the leaders of these nations said Sunday at the end of their two-day summit in Rome.

But the leaders, some of whom represent the largest greenhouse gas emitters, did not set a common or specific date for achieving global net-zero emissions or phasing out unabated coal power in general, boding ill for the crucial United Nations COP26 climate conference that began Sunday in Glasgow, Scotland.

"We commit to mobilize international public and private finance to support green, inclusive and sustainable energy development, and we will put an end to the provision of international public finance for new unabated coal power generation abroad by the end of 2021," the declaration issues by the leaders said.

The commitment follows a similar decision by the Group of Seven top industrial economies in June, and it shows progress by the G-20 since July when ministerial-level meetings on the subject hit a wall. China's statement in September that it would stop funding new overseas coal power might have been a crucial development.

The G-20 national leaders also committed to hold the global average temperature increase to "well below 2 C and to pursue efforts to limit it to 1.5 C above pre-industrial levels."

But in an ominous sign for the COP26 summit, the leaders failed to reach agreement on detailed deadlines for other closely watched commitments, such as a unified date for achieving global net-zero carbon emissions and phasing out unabated coal power domestically, which is seen as key to reduce emissions.

British Prime Minister Boris Johnson, in a news conference, offered a more optimistic assessment.

"I think that we've made reasonable progress. We have certainly not gone into reverse," he said. "I think we've inched forward, we've put ourselves in a reasonable position for COP in Glasgow, but it is going to be very, very difficult in the next few days."

The G-20 represents 80% of the world's gross domestic product, 60% of the population and -- crucially -- an estimated nearly 80% of greenhouse gas emissions. Ahead of COP26, it was hoped the group -- which includes countries such as the U.S., China, Japan, India, Germany, the U.K. and Brazil -- would take leadership on tackling climate change.

"We will accelerate our actions across mitigation, adaptation and finance," the 20-page leaders declaration states, "acknowledging the key relevance of achieving global net-zero greenhouse gas emissions or carbon neutrality by or around mid-century and the need to strengthen global efforts required to reach the goals of the Paris Agreement."

G-20 leaders toss a coin into Rome's iconic Trevi Fountain on the sidelines of the G-20 summit in the Italian capital on Oct. 31.   © Reuters

The text suggests that leaders could not agree on the more ambitious 2050 net-zero emissions target advocated by the U.K., the COP26 host.

Johnson said the "mid-century" commitment "is a function, really, of the gap between some colleagues and others. Some countries, as you know, have made commitments to 2060 rather than 2050 ... What we want to do is bring those commitments earlier."

Just 12 of the G-20 members have committed to reaching net-zero emissions by 2050 or earlier, he said.

Many countries now have a 2050 target. But those that have a 2060 target include China, the world's largest emitter, and Russia, which ranks in the top five. Others, such as India, the third-largest emitter, have not yet committed to a specific date.

The Asia-Pacific region is critical for reducing global emissions because many of the countries have both a heavy dependence on coal and a growing need for energy as their economies expand. According to BP's Statistical Review of World Energy 2021, the Asia-Pacific is the only region where coal is the dominant fuel being consumed.

Johnson acknowledged the lack of an agreement on phasing out domestic coal use.

"I think, really, that is the important question," he said. "And that's why going into Glasgow we need to make more progress on domestic coal. And I think it can be done."

Throughout the leaders document, the tension and divide among countries over climate issues and solutions can be seen in the language noting that pledges and statements will "take into account national circumstances," reflecting the differing energy needs and development levels of the G-20 countries.

How to achieve vaccine equity between rich and poor countries was another topic of discussion. The G-20 leaders agreed to "refrain from [World Trade Organization] inconsistent export restrictions and to increase transparency and predictability in the delivery of vaccines."

In line with World Health Organization recommendations to vaccinate at least 40% of the population in all countries by the end of 2021, and 70% by mid-2022, the G-20 said it would "take steps to help boost the supply of vaccines and essential medical products and inputs in developing countries and remove relevant supply and financing constraints."

G-20 health ministers were tasked with exploring and monitoring such steps, but no concrete measures or hard deadlines were set out. The countries committed to "substantially increase the provision of and access to" vaccines, therapeutics and diagnostics.

As an energy crisis sweeps the world, the G-20 cited the importance of maintaining undisrupted flows of energy.

"The G-20 in collaboration with the International Energy Forum will facilitate a dialogue between producers and consumers to bolster the efficiency, transparency and stability of the energy markets," the declaration stated.

The G-20 leaders hailed an agreement on a global minimum tax rate of 15% for multinational enterprises starting in 2023 as a "historic achievement."

Tristen Naylor, assistant professor of politics and history at the University of Cambridge, told Nikkei Asia: "On the big issues, the pandemic, the global economy, and climate change there are no surprises, neither good nor bad. That said, the conclusions on climate change concerns me, because it shows G-20 aren't collectively showing the sort of leadership the world badly needs. It doesn't bode well for COP26."

"The question I ask myself is, if the summit hadn't happened, what would be different? I think not much. This declaration doesn't indicate that the weekend really moved things along much at all," Naylor said. "It's really tough to have the difficult discussions that need to be had when key leaders, like those of Russia and China, weren't there, so it was difficult from the get go."

At the G-7 summit in June, leaders stated their support for the Tokyo 2020 Olympics. The G-20 said it would "look ahead" to the Beijing Winter Olympics and Paralympics in 2022 "as opportunities for competition for athletes from around the world, which serves as a symbol of humanity's resilience."

The next G-20 leaders summits will be held in Asia: in Indonesia in 2022, and in India in 2023.