President Biden has unveiled plans to cut US carbon emissions by between 50-52% by 2030 from 2005 levels.
The US confirmed the target, which is twice as tough as its previous commitment, at Earth Day, a virtual summit of 40 global leaders.
“This is a decisive decade,” said the US President.
“The steps our countries take between now and Glasgow will set our world up for success. This is a moment of extraordinary possibility”.
Other countries have been unveiling new targets ahead of the summit with the EU announcing a target of a 55% reduction yesterday and the UK going further with a plan for a 78% cut by 2035 earlier in the week.
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Reports from the summit suggested that President Biden is hoping to use the new target to get other large fossil fuel users such as China, Brazil and India to agree to significant reductions in their carbon emissions.
China has set a net-zero emissions goal by 2060 but observers suggested that President Xi attending the summit might indicate some change in its targets as well.
President Biden, who is hosting the summit, is also trying to restore US leadership in the carbon emission arena after predecessor Donald Trump withdrew the country from the Paris climate pact.
Commentators had predicted that the US would go for a big target reduction ahead of the meeting.
Dutch bank ING said this morning that a consensus was forming around a 50% cut by 2030 and zero emissions by 2050.
The US gave no details on how it would meet its target with some scepticism that it is possible given the political division over energy policy in the country.
Possible options include a carbon border tax, which the EU is considering, or tariffs on countries that do not have similar carbon reduction targets or even direct restrictions on power plants.
Biden has already announced a US$2trn infrastructure spending programme, that with green energy incentives might also take it a long way towards the target while avoiding a conflict over reductions in the use of coal, oil and gas.
A UN Climate Summit will take place in Glasgow later this year focused on measures to tackle climate change to be hosted by PM Boris Johnson.
Shares in energy companies were little changed on the pledge.