The governor of New York, the multi-billionaire former Republican Michael Bloomberg, has thrown his support behind Barack Obama to be returned to the White House.
He wrote the announcement in a section of the Bloomberg News website.
He said Obama had taken significant steps to reduce carbon consumption, whereas the Republican challenger Mitt Romney has backtracked on climate change.
Bloomberg’s comments came after his city and much of the US eastern seaboard were devastated by superstorm Sandy.
Obama said he was honoured to have Mayor Bloomberg’s endorsement.