US President Donald Trump has withdrawn the US from dozens of international organisations, including many that work to combat climate change.

Among the 66 groups, nearly half of them are bodies of the United Nations, including the UN Framework Convention on Climate Change - a treaty that underpins all international efforts to combat global warming.

The White House said the decision was taken because those entities "no longer serve American interests" and promote "ineffective or hostile agendas".

Trump has already stripped many multilateral organisations he dislikes of funds and previously rejected the scientific consensus of man-made climate change as a "hoax".

The memorandum was signed on Wednesday after a review into causes that the White House said were "a waste of taxpayer dollars".

"These withdrawals will end American taxpayer funding and involvement in entities that advance globalist agendas over US priorities," it said in a statement.

It added that many of the organisations promoted "radical climate policies, global governance and ideological programs that conflict with US sovereignty and economic strength".

The UN's Intergovernmental Panel on Climate Change (IPCC), an expert body that assesses climate science worldwide, was also included on the list.

Other UN organisations affected included those working on peace and democracy, family planning, maternal and child health, and sexual violence in conflict.

While the US Constitution allows presidents to join treaties "provided two thirds of Senators present concur", it does not specify what happens if they were to withdraw, which means Trump's move could face legal challenges.

A member of a US-based non-profit advocacy group, the Union of Concerned Scientists, described the step as a "new low".

Senior policy director Rachel Cleetus told AFP news agency it was another sign that the administration, which she described as "authoritarian" and "anti- science", was determined to sacrifice people's wellbeing and destabilise global cooperation.

Last year, Trump once again withdrew the US from the Paris climate agreement - the world's most important effort to tackle rising temperatures - and declined to send a delegation to the COP30 climate summit in Brazil.