Prime Minister Jacinda Ardern says New Zealand is likely to impose new travel restrictions after the United States banned all travellers from Europe.

US President Donald Trump shocked the world and stockmarkets with his announcement on Thursday afternoon (NZ Time) that all non-resident travellers from Europe would be banned for 30 days in an attempt to stop the growth of coronavirus cases.

Asked about his actions and whether New Zealand needed to step up its own settings, Ardern said New Zealand was reviewing its travel restrictions every 24 hours - and she expected they would be getting tougher on Friday.

COLLETTE DEVLIN/STUFF Health Minister David Clark and Finance Minister Grant Robertson react to Trump's travel ban.

"We have been continually looking out at the environment we are in and trying to plan for one step ahead so we can slow transmission," Ardern said.

"I expect that we will see further border restrictions in New Zealand...Yesterday we moved on further border restrictions, I expect it will be the same tomorrow."

She noted an outbreak in the US and said that might contribute to further restrictions.

"We are seeing outbreaks within that primary hotspot where we already have border controls - Italy. Now of course we are seeing outbreaks in the United States. We need to factor all of that in in the continual advice we are getting on our border restrictions."

The current travel restrictions ban all non-residents from China and Iran, and force all travellers from South Korea or Italy to self-isolate for 14 days.

The White House US President Donald Trump suspends European travel for 30 days amid virus outbreak.

Opposition leader Simon Bridges called on her to ban all travellers from Italy and South Korea in response to the news.

But Health Minister David Clark said the reality of the self-isolation requirement meant almost all travel from those places had stopped anyway.

Asked about a potential travel ban on all of Europe, Clark said he would base his view entirely on the views of scientific and health advice from his officials, who he said were monitoring the US and Europe and their actions.

Finance Minister Grant Robertson said it was likely the 30-day ban would affect global confidence.

"Economically these are challenging times. Each event we look at and we look at consequences for New Zealand."

He said it was likely the domestic portion of a stimulus package for the tourism sector would likely have to be stepped up as global travel reduced.

Robertson is working on two economic packages - one shorter term targeted business continuity package with wage subsidies for businesses and a wider economic stimulus package in case of a sustained downturn.

He told the Wellington Chamber of Commerce on Thursday that the virus showed the need to diversify New Zealand's economy.

"It will include measures to help us diversify our export and import markets — one of many lessons we can learn from this," Robertson said.

China accounts for over a quarter of our exports.

New Zealand currently has five confirmed cases of coronavirus with no confirmed community outbreak.

Prior to Trump's move on Thursday German chancellor Angela Merkel made waves when she predicted that two thirds of Germans could become infected.

"The consensus among experts is that 60 to 70 percent of the population will be infected as long as this remains the situation."