There are now more new cases of the coronavirus reported each day outside China than inside the hardest-hit country, the World Health Organisation (WHO) said on Wednesday.

“Yesterday, the number of new cases reported outside China exceeded the number of new cases in China for the first time,” WHO chief Tedros Adhanom Ghebreyesus told diplomats in Geneva, according to a written version of his speech.

The UN health agency put the number of new cases in China at 411 on Tuesday and those registered outside the country stood at 427.

Governments worldwide are scrambling to prevent the spread of the new coronavirus after a surge of infections in Italy, Iran and South Korea.

Tedros said the “sudden increase of cases” in those countries was “deeply concerning”, adding that a WHO team would travel to Iran this weekend to evaluate the situation.

While new case numbers and deaths are dwindling at the disease epicentre in China, the country remains by far the hardest hit.

Tedros said that as of Wednesday morning, 78,190 cases of COVID-19 had been registered in China, including 2,718 deaths. That compares with 2,790 cases and 44 deaths reported across 37 other countries.

But WHO has said the epidemic in China peaked on February 2 and has been declining since.

Bruce Aylward, who headed a WHO-backed expert mission to China, hailed the drastic quarantine and containment measures taken by Beijing, saying the country had “changed the course” of the outbreak.

But he told reporters in Geneva that other nations were “simply not ready”.

In Wednesday's speech, Tedros acknowledged that the hike in cases outside China had prompted a push for a pandemic to be declared.

“We should not be too eager to declare a pandemic,” he said, stressing that such a declaration could “signal that we can no longer contain the virus, which is not true.”

“We are in a fight that can be won if we do the right things.” But he insisted that WHO would not hesitate to declare a pandemic “if it is an accurate description of the situation.”

“I am not downplaying the seriousness of the situation, or the potential for this to become a pandemic, because it has that potential,” he said.

“All countries, whether they have cases or not, must prepare for a potential pandemic.“

Iran raises its death toll to 19

Iran's president said Tehran has no immediate plans to quarantine cities over the new coronavirus rapidly spreading across the country, even as the country suffers the highest death toll outside of China with 19 killed amid 139 cases confirmed on Wednesday.

President Hassan Rouhani went on to acknowledge that it may take one, two or three weeks to get control of the virus in Iran, linked to most of the over 210 confirmed cases of the virus now spread across the Mideast.

That comes after the top official in charge of Iran's response to the coronavirus tested positive for the illness after a day earlier trying to downplay the disease.

Still, Rouhani sought to portray the virus crisis in terms of Iran's tense relations with the US

"Coronavirus must not be turned into a weapon for our enemies to halt work and production in our country," Rouhani said, according to a transcript posted to the Iranian presidency's website.

Iranian state television reported on Wednesday that 19 people have been killed by the new coronavirus amid 139 confirmed cases in the country so far.

The announcement by a state TV anchor came as Health Ministry spokesman Kianoush Jahanpour urged Iranians to avoid nonessential travel, particularly to the hard-hit provinces of the country such as Gilan and Qom.

Wednesday's figures still showed no cases confirmed in the Iranian city of Mashhad, though a number of cases now reported in Kuwait are linked to Mashhad.

In Tehran overnight, workers disinfected mass transit buses and the capital's underground metro system, removing overhead handles in an effort to limit areas the virus could be picked up from.

Traffic again appeared lighter on Tehran's normally gridlocked roads amid a winter rain, as signs warned Iranians not to touch surfaces in crowded areas.