Prime Minister Jacinda Ardern said she did not agree with US President Donald Trump's stated reasons for defunding the World Health Organsation, and said it would be key in the fight against coronavirus.

Trump announced on Wednesday that he would suspend American funding to the WHO as the US "reviewed" its role in the coronavirus outbreak.

The US is the largest single funder of UN-organised body, spending between $400 and $500m a year - over ten per cent of the total budget.

GETTY IMAGES "At a time like this where we need to be sharing information where we need to have advice that we can rely on the WHO has been doing that," Ardern said.

Trump said the WHO had failed to contain the virus within China because of "political correctness" and had pushed back against travel bans.

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He said the organisation had "failed in its basic duty and it must be held accountable."

Asked if these arguments had merit on Wednesday, Ardern simply responded "no".

She said the position of New Zealand was that the WHO was incredibly important.

"At a time like this where we need to be sharing information where we need to have advice that we can rely on the WHO has been doing that," Ardern said.

New Zealand spent just over $2m supporting the WHO at the last budget.

Health Director General Dr. Ashley Bloomfield worked at the WHO in Geneva in 2011 on non-communicable diseases.

He said on Wednesday that the WHO would be key in fighting coronavirus.

"The global response to this pandemic will require a strong World Health Organisation so it behoves all of us I think to - and New Zealand I know will continue to play its part supporting the organisation both globally and in our region in the Pacific."

While Trump's move has come under widespread fire, the WHO have been criticised by many for its response to Covid-19, particularly over whether it was too trusting of China.

Japanese deputy prime minister Taro Aso said it had close enough ties to China that some people were describing it as the "Chinese Health Organisation". It has also come in for criticism from Taiwan.

United Nations Secretary-General Antonio Guterres said it was "not the time" to over-examine the WHO response.

"Once we have finally turned the page on this epidemic, there must be a time to look back fully to understand how such a disease emerged and spread its devastation so quickly across the globe, and how all those involved reacted to the crisis. The lessons learned will be essential to effectively address similar challenges, as they may arise in the future,' Gutterres said in a statement.

"But now is not that time."

"As it is not that time, it is also not the time to reduce the resources for the operations of the World Health Organisation or any other humanitarian organisation in the fight against the virus."