Nearly 90 countries have joined a US- and EU-led effort to slash emissions of the potent greenhouse gas methane 30 per cent by 2030 from 2020 levels.
The pact is aimed at tackling one of the main causes of climate change, a senior official for the Biden administration says.
The partnership will be formally launched later on Tuesday.
Methane is the main greenhouse gas after carbon dioxide.
It has a higher heat-trapping potential than CO2 but breaks down in the atmosphere faster, meaning cutting methane emissions can have a rapid impact on reining in global warming.
The Global Methane Pledge, which was first announced in September, now includes half of the top 30 methane emitters accounting for two-thirds of the global economy, according to the official.
Among the new signatories to be announced on Tuesday is Brazil – one of the world’s five biggest emitters of methane.
China, Russia and India, also top-five methane emitters, have not signed on to the pledge, while Australia has ruled out reducing methane emissions in line with the group’s target.
Since it was first announced in September with a handful of signatories, the United States and European Union have worked to get the world’s biggest methane emitters to join the partnership.
Roughly 60 countries signed up only last week, after a final diplomatic push from the United States and EU ahead of the COP26 summit
While it is not part of the formal UN negotiations, the methane pledge could rank among the most significant outcomes from the COP26 conference, given its potential impact in holding off disastrous climate change.
A UN report in May said steep cuts in methane emissions this decade could avoid nearly 0.3C of global warming by the 2040s.
Failing to tackle methane, however, would push out of reach the Paris Agreement’s aim to limit global temperature rise to 1.5C above preindustrial levels and avoid the worst impacts of climate change.
The 30 per cent methane cut would be jointly achieved by the signatories, and cover all sectors.
Key sources of methane emissions include leaky oil and gas infrastructure, old coal mines, agriculture and landfill sites.
If fulfilled, the pledge is likely to have the biggest impact on the energy sector, since analysts say fixing leaky oil and gas infrastructure is the fastest and cheapest way to curb methane emissions.
The United States is the world’s biggest oil and gas producer, while the EU is the biggest importer of gas.