Prime Minister Jacinda Ardern and other New Zealand lawmakers are hitting back at President Donald Trump in unusually blunt terms over his comments comparing the coronavirus outbreak there to the US.

"Obviously it's patently wrong," Ardern told reporters on Tuesday in response to Trump saying there had been a "huge surge" in her country.

Speaking to supporters in Michigan on Monday, Trump tried to defend his handling of the pandemic by highlighting other countries who are experiencing sudden upticks.

“When you look at the rest of the world ... now all the sudden, a lot of the places that they were using to hold up, they’re having a big surge,” Trump said. “They were holding up names of countries, and now they’re saying, ‘Whoops!’

"In fact, even New Zealand," Trump said.

Following several months of no new COVID-19 infections in New Zealand, the country last week began seeing several cases emerge in the city of Auckland. That small outbreak, the source of which is under investigation, prompted Ardern to plunge the city back into lockdown.

According to public broadcaster Radio New Zealand, there are currently 90 active cases of the virus in all of New Zealand, which has a total population of 4.8 million people.

"You see what's going on in New Zealand. They beat it [the virus], they beat, it was like front-page [news] they beat it because they wanted to show me something," Trump said Monday.

"The problem is [there is a] big surge in New Zealand. You know it's terrible - we don't want that."

But New Zealand politicians called Trump out, saying it was not fair or accurate to compare their number of new cases - nine on Monday and 13 on Tuesday, according to Radio New Zealand - with the US.

"Obviously I don't think there's any comparisons between New Zealand's current cluster and the tens of thousands of cases that are being seen daily in the United States," said Ardern.

"Every country is experiencing its own fight with COVID-19," she added. "It is a tricky virus but not one where I would compare New Zealand's current status to the United States.

"New Zealand's nine cases in a day does not compare to the United States' tens of thousands," she said.

On Monday, the US recorded almost 38,000 new cases of COVID-19 and 406 deaths.

Other senior members of Ardern's government also pushed back against Trump - in strong language rarely seen from a US ally.

"The American people can work out that we have for a whole day what they every 22 seconds of a day," said Deputy Prime Minister Winston Peters. "That speaks for itself."

"We know by now to take everything Donald Trump says with a grain of salt," said Greens leader James Shaw. "But coming from the leader of a country that had 42,000 new cases just yesterday, I think it's an absurd comparison."

Ardern announced on Monday that she would postpone her country's September election by four weeks due to the outbreak.