Bloomberg's intervention aims to ensure the United Nations Framework Convention on Climate Change (UNFCCC) remains fully funded despite the United States halting its contributions.

Washington typically provides 22 percent of the UNFCCC secretariat's budget, with the body's operating costs for 2024-2025 projected at 88.4 million euros ($96.5 million).

The secretariat is tasked with supporting the global response to climate threats, and organizes international climate conferences, the next of which will be COP30 held in Brazil in November.

"From 2017 to 2020, during a period of federal inaction, cities, states, businesses, and the public rose to the challenge to uphold our nation's commitments -- and now, we are ready to do it again," Bloomberg, who serves as the UN special envoy on climate ambition and solutions, said in a statement.

This marks the second time Bloomberg, the former mayor of New York, has stepped in to fill the gap left by US federal disengagement.

In 2017, following the Trump administration's first withdrawal from the Paris accord, Bloomberg pledged up to $15 million to support the UNFCCC.

He also launched "America's Pledge," an initiative to track and report US non-federal climate commitments, ensuring the world could monitor US progress as if it were still a fully committed party to the Paris Agreement.

Bloomberg reiterated his commitment to upholding US reporting obligations this time as well.

"Contributions like this are vital in enabling the UN Climate Change secretariat to support countries in fulfilling their commitments under the Paris Agreement and advancing a low-emission, resilient, and safer future for all," said UN climate chief Simon Stiell.

Laurence Tubiana, a key architect of the Paris climate accord, said Bloomberg's "generous donation will allow the world to maintain a vital forum for cooperation on the fundamental challenge of our time, which no country can solve alone or afford to ignore."

Trump on Monday announced the United States' withdrawal from the Paris accord, which is managed by the UN climate change body, brings together almost all the world's nations and aims to keep global average temperature rise below a certain threshold.

The president also signed an executive order directing the United States to withdraw from the UN's World Health Organization, which had a budget of $7.89 billion in 2022-2023, with Washington contributing 16.3 percent of the total.