President Joe Biden hopes to rally the world on climate as he unveils more ambitious US commitments Thursday at a summit that is expected to see a slew of new promises.

Just three months into office, Biden will welcome 40 leaders for the two-day virtual Earth Day summit, heralding a US return to the climate frontlines amid mounting worries over the rapid heating of the planet.

Green groups expect that Biden, who is pushing a green-friendly $2 trillion infrastructure package at home, will roughly double US targets for slashing emissions responsible for climate change over the next decade.

Biden hopes the new US goal will prompt other leaders "to make announcements to raise their ambition" as well, an administration official said.

US President Joe Biden is expected to raise climate ambitions with an Earth Day summit US President Joe Biden is expected to raise climate ambitions with an Earth Day summit Photo: AFP / Brendan Smialowski

Japanese Prime Minister Yoshihide Suga on a visit to Washington last week indicated he was planning a new commitment.

And Canadian Prime Minister Justin Trudeau will pledge to reduce carbon emissions by 40-45 percent by 2030 from 2005 levels, hastening the 30 percent commitment under the Paris Agreement, public broadcaster Radio-Canada said, citing unnamed sources.

China confirmed that President Xi Jinping will take part and give an "important speech" -- his first summit, even if virtual, with Biden as president amid soaring tensions between the two powers on issues from human rights to trade to defense.

China is by far the largest carbon producer and with the United States emits around half of the pollution responsible for climate change, meaning any solution is impossible without both countries.

China last year promised to go carbon neutral by 2060 with emissions peaking at around 2030 but it has also kept up reliance on coal, the dirtiest form of energy, and bristled at EU-led calls for a carbon tax that would hit its exports.

Former coal miner Liu Sheng showing an X-ray of his lungs at his home near the Datai coal mine in Mentougou, west of Beijing, in December 2019 Former coal miner Liu Sheng showing an X-ray of his lungs at his home near the Datai coal mine in Mentougou, west of Beijing, in December 2019 Photo: AFP / GREG BAKER

Former president Barack Obama, after negotiating the 2015 Paris Agreement, promised that the United States would reduce emissions by 26-28 percent by 2025 compared with 2005 levels.

Obama's successor Donald Trump pulled out of the Paris accord, calling it unfair to the world's largest economy, but the United States is still largely on track to meet Obama's goal thanks to continued commitment at the level of states, especially California, and a sharp drop in industrial production last year during the Covid-19 pandemic.

But studies say far more needs to be done to meet the Paris goal of checking warming at two degrees Celsius (5.4 Fahrenheit) above pre-industrial levels, let alone its aspiration of no more than 1.5 Celsius.

Activists from the Extinction Rebellion climate action group and local campaigners block the entrance to the site of the Bradley coal mine in the northeasern English county of Durham in February 2020 Activists from the Extinction Rebellion climate action group and local campaigners block the entrance to the site of the Bradley coal mine in the northeasern English county of Durham in February 2020 Photo: AFP / Paul ELLIS

A UN study late last year found that the world is on track to see warming by three degrees -- a level at which the planet is forecast to see many glaciers and ice caps melt, low-lying areas submerged and increasingly severe droughts, floods and disasters that could trigger mass migration.

Treasury Secretary Janet Yellen said in a speech that the United States still requires "substantially more" than the sum Biden has budgeted -- and which many Republicans oppose -- to go carbon neutral.

"Private capital will need to fill most of that gap," she said.

Trump also blocked US contributions to the Green Climate Fund, set up by the Paris Agreement to help efforts by poor nations that bear little responsibility for the warming planet.

The United States contributed $1 billion of the $3 billion Obama promised before he left office. Biden has requested $1.2 billion from Congress to make up some of the arrears.

Britain on Tuesday announced the most ambitious target of any major economy, saying it will slash emissions by 78 percent by 2035 from 1990 levels.

Prime Minister Boris Johnson announced the commitment as Britain prepares to host a UN conference in November in Glasgow which is aimed at raising ambitions beyond Paris.

Following the announcement by former member Britain, the European Union in marathon talks approved a law that confirms the 27-nation bloc's commitment to reduce carbon by at least 55 percent by 2030 compared with 1990 levels.

Some European parliament members had pushed for greater ambition but European leaders, the historic champions of global climate efforts, hailed what they said was at last a legal framework to achieve targets.

"This climate deal is a game changer," the chair of the European Parliament's environmental commission, Pascal Canfin, told reporters.

Environmentalists are urging nations to take immediate action, not just to make longer-term promises.

"To get closer to the 1.5 pathway, significant political will and action are required," said Jennifer Morgan, executive director of Greenpeace International.

"The world's richest countries must do more than just halve their emissions by 2030, having profited from extractive and polluting industries leading to the climate crisis."