US President Joe Biden will pledge on Thursday to cut US greenhouse gas emissions by half by the end of the decade compared to 2005 levels, officials said.
The promise will come at an online summit Biden is convening with 40 world leaders aimed at getting the major economies to set more ambitious carbon-slashing goals, the DPA news agency reported.
The two-day meeting, which opens later on Thursday, is seen as important preparation ahead of the next UN climate crisis conference, to be held in Glasgow in November.
Chinese President Xi Jinping will join the video conference, in what is seen as a goodwill gesture after a rocky start to Beijing's relationship with the new administration in the White House.
China is the world's biggest emitter of carbon dioxide gases, followed by the US, India and Russia, according to the International Energy Agency, a Paris-based group.
A Chinese Foreign Ministry spokesperson said Xi would deliver an "important speech" to his counterparts.
Biden will announce his intention to cut emissions by between 50 per cent and 52 per cent at the economy-wide level, a White House statement said.
The pledge doubles the promise made by former President Barack Obama, but gives the current administration five more years to meet its goal.
In 2015, the US had committed to reducing greenhouse gas emissions by 26-28 per cent by 2025, compared to 2005 levels, as a contribution to the global Paris Agreement.
One of Biden's first acts in office was to return his country to the 2015 climate accord, which his predecessor, Donald Trump, had pulled from.
The White House outlined several paths to help meet the 2030 goal, but offered few details. It said cutting tailpipe emissions, boosting vehicle efficiency standards, and investing in transportation infrastructure and new technologies would help get the US on track.
Another priority is to focus on heavy cuts to emissions of methane - a major contributor to global warming.
Biden had previously announced the goal of reaching "100 per cent carbon pollution-free electricity by 2035" and a net-zero US emissions economy by no later than 2050.
On Wednesday, the European Union officially committed to at least a 55-per-cent reduction in emissions by 2030 compared to 1990 levels.
Britain, meanwhile, said this week it is aiming by 2035 to reduce emissions by at least 78 per cent below 1990 levels.
British Prime Minister Boris Johnson is expected to expand further on his pledge at Thursday's event and urge other countries to use 2021 as a time to set their ambitious plans.
"If we actually want to stop climate change, then this must be the year in which we get serious about doing so. Because the 2020s will be remembered either as the decade in which world leaders united to turn the tide, or as a failure," Johnson is expected to say in a speech seen by dpa.
Other world leaders scheduled to participate at the summit include Russian President Vladimir Putin, Indian Prime Minister Narendra Modi, Brazilian President Jair Bolsonaro, French President Emmanuel Macron and German Chancellor Angela Merkel.
Japanese Prime Minister Suga Yoshihide said on Thursday that his country will aim to reduce greenhouse gas emissions by 46 per cent from the 2013 levels by 2030, according to broadcaster NHK.
Yoshihide also said that Japan wants to be carbon-neutral by 2050.
More than 120 countries have made net zero commitments to date, covering 65 per cent of global carbon emissions.
But scientists say the world is not collectively moving fast enough to avert the worst effects of climate change by keeping warming to below 2 degrees above pre-industrial levels.
The World Meteorological Organization said in January that Earth is on pace for "a catastrophic temperature rise of 3 to 5-degree Celsius this century" unless urgent action is taken.