US President Joe Biden told the United Nations General Assembly on Tuesday that his country would "double" its contribution to international climate financing towards the goal of mobilizing $100 billion for vulnerable nations.

Experts said the announcement would take the US contribution to the commitment, made by developed countries ahead of the 2015 Paris agreement, to approximately $11.4 billion annually.

"This will make the United States a leader in public climate finance," Biden told world leaders in New York, saying he would work with Congress to achieve the goal.

The announcement comes weeks before the next major UN climate conference, COP26 in Glasgow.

"Strongly welcome @POTUS further doubling climate finance commitment to over $11bn by 2024," said British lawmaker Alok Sharma, who will preside over COP26.

"This demonstrates the increased ambition required to deliver on the $100bn/year goal," he wrote. "We must build on this momentum."

The accord calls for public, multilateral and private financing of $100 billion a year from 2020-2025 to assist poor nations already coping with floods, heatwaves, rising seas and superstorms made worse by climate change.

Last week, the OECD confirmed that only $79.6 billion was mobilized in 2019, leaving a more than $20 billion shortfall.

Climate advocacy groups welcomed the announcement. 

"President Biden's commitment to scaling up international climate finance to $11.4 billion per year by 2024 is a welcome and much-needed sign that the United States is finally taking its global climate responsibilities seriously," said Rachel Cleetus, of the Union of Concerned Scientists.

"Climate vulnerable nations -- particularly low- and middle-income countries -- are already reeling from an unprecedented onslaught of climate-related disasters and desperately need financial support to adapt and build resilience to worsening impacts."

The announcement was one of several demonstrating the United States' renewed commitment to global engagement following the Trump era.

Biden said the US, already the world leader in donating Covid-19 vaccines, will announce "additional commitments" on fighting Covid-19 when the White House hosts a summit on the pandemic on Wednesday, and a $10 billion commitment to end hunger at home and abroad.