US media multi-billionaire Michael Bloomberg, former Mayor of New York and owner of the eponymous news service, said he'll pay the outstanding US contribution to the funding for the Paris Agreement on climate change after President Donald Trump announced the US was withdrawing from the pact.

Michael Bloomberg

Bloomberg, in a statement issued by his charity arm, Bloomberg Philanthropies, said he's offering $15 million to the United Nations to support the UN Framework Convention on Climate Change Secretariat, which would work to help signatory countries implement their commitments.

Bloomberg, ranked the eighth richest man in the world by Forbes Magazine, is worth $50.2 billion, mainly due to his 88 percent stake in his media and financial data company.

"Americans are not walking away from the Paris Climate Agreement," Bloomberg said. "Just the opposite – we are forging ahead."

Bloomberg, 75, is a UN Special Envoy for Cities and Climate Change.

"Americans will honor and fulfil the Paris Agreement by leading from the bottom up – and there isn't anything Washington can do to stop us," he said.

He said US mayors, governors and business leaders "from both political parties are signing onto a statement of support that we will submit to the UN – and together we will reach the emission reduction goals the US made in Paris in 2015."