Donald Trump COVID-19: Jacinda Ardern hopes US President has 'speedy recovery'

New Zealand Prime Minister Jacinda Ardern has wished US President Donald Trump and First Lady Melania Trump a "speedy recovery".

"We have seen now several world leaders who have been affected by COVID-19 and I know that I stand with others in wishing all the best. This is, obviously, a virus that has globally had a devastating impact," the Labour leader said on Saturday.

Ardern was out campaigning in Auckland when she made her comments. The city, New Zealand's most populated, was in August sent into lockdown after an outbreak of the virus, but it has since had restrictions lifted. While the US continues to struggle in its fight with COVID-19, New Zealand is seeing very few cases each week - most returnees.

Previous world leaders to contract the virus, which has killed more than one million worldwide and infected nearly 35 million, include UK Prime Minister Boris Johnson and Brazilian President Jair Bolsonaro.

When Johnson became unwell, Ardern texted him New Zealand's best wishes. But she says she doesn't have the US President's personal number, hence why she asked for her thoughts to be expressed to him via official channels. 

"New Zealand would wish anyone experiencing COVID a speedy recovery and our very best wishes and all the best," she said.

It is too early to say what the implications of the diagnosis could have on New Zealand, Ardern told reporters. It comes just a month out from the US election. 

"We still haven't even seen out of the administration the likely effect they believe it will have on the election campaign. Of course, we haven't seen an election date moved before and it's quite a process for that to happen," she said.

"So at this stage, I'd say it would all be highly speculative, we just haven't heard anything official from the White House in that regard."

Trump and his wife were diagnosed on Friday with the illness after a positive test result was received for the President's aide Hope Hicks.

On Saturday morning (NZT), he was moved to Walter Reed Medical Centre, which officials said was only a precaution. In a video filmed before he travelled there via helicopter, Trump said he was "doing very well".

The President has been given a single eight-gram dose of Regeneron's polyclonal antibody cocktail as well as zinc, vitamin D, famotidine, melatonin and aspirin, according to his physician.

While the White House has downplayed concern, a CNN source said on Saturday the situation was "serious" and Trump was fatigued, tired and having some trouble breathing. 

Other current and former world leaders have sent their best wishes to Trump, including Barack Obama, Bill Clinton, Boris Johnson and Scott Morrison.