Tedros Ghebreyesus said the spread of the virus around the world is not yet at pandemic stage, but acknowledged it has the potential to become one.

The WHO no longer uses an official scale to declare a pandemic, although spokeswoman Margaret Harris said it would start to use the term in communications if it believes a pandemic is reached.

Speaking in Geneva, Dr Ghebreyesus said the focus must still be on containing the virus in individual countries, adding that the world is not yet seeing "large-scale severe disease or death".

Prof Hunter said the current public health strategy in the UK of trying to contain the virus was the right one, as the number of cases here is still low.

He said the WHO was "encouraged by the continued decline in cases in China", though more 77,362 cases have been declared there, including 2,618 deaths.

Coronavirus: Four more people in UK test positive for deadly disease

For people with mild disease, recovery time is about two weeks, while people with severe or critical disease recover within three to six weeks.

Outside China, there are now 2,074 cases confirmed in 28 countries, and 23 deaths, including a rapid rise in cases in Italy, South Korea and Iran, he added.

"There's a lot of speculation about whether these increases mean that this epidemic has now become a pandemic.

"WHO has already declared a public health emergency of international concern - our highest level of alarm - when there were less than 100 cases outside China, and eight cases of human-to-human transmission.

"Our decision about whether to use the word 'pandemic' to describe an epidemic is based on an ongoing assessment of the geographical spread of the virus, the severity of disease it causes and the impact it has on the whole of society.

"For the moment, we are not witnessing the uncontained global spread of this virus, and we are not witnessing large-scale severe disease or death.

"Does this virus have pandemic potential? Absolutely, it has. Are we there yet? From our assessment, not yet."

Another leading expert has meanwhile said the global coronavirus pandemic is not inevitable, but is looking more likely as the virus continues to spread.

Paul Hunter, professor in medicine at the University of East Anglia (UEA), said the current situation in countries such as South Korea - where more than 600 people have been infected - suggested the world was heading for a pandemic.

He said: "It's not inevitable, but I wouldn't bet against it."

Prof Hunter said the current public health strategy in the UK of trying to contain the virus was the right one, as the number of cases here is still low.

"In the UK, the containment policy is still the right course of action but for how long, I don't know," he said.

"It's probably doable up to a few hundred cases."

Prof Hunter said it was unclear how many more cases the UK could see.

So much was still unknown about the virus, including whether it is spread easily by people with no apparent symptoms, he added.

"We still don't know how worried to be about asymptomatic people," he said.

"There is still uncertainty about how asymptomatic people are, and how they contribute to the spread of infection."

World must prepare for potential coronavirus pandemic, warns health chief