The World Health Organisation will decide on Thursday whether to declare a global emergency over the outbreak of a new flu-like virus spreading in and beyond China.
If it does so it will be only the sixth international public health emergency to be declared in the last decade.
"The decision is one I take extremely seriously and one I am only prepared to make with appropriate consideration of all the evidence," WHO director-general Tedros Adhanom Ghebreyesus said.
"This is an evolving and complex situation," he added. "Our team in China is working with local experts and officials to investigate the outbreak."
He was speaking after the WHO held a day-long meeting of an independent panel of experts in Geneva on Wednesday.
Deaths from China's new coronavirus virus rose to 17 on Wednesday with more than 540 cases confirmed, increasing fears of contagion from an infection suspected to originate from illegally traded wildlife.
The WHO's head of emergencies programme, Mike Ryan, said the priority now was to find the roots of how the virus is passing between people.
"We are in agreement with Chinese authorities who have been clear and transparent that there is evidence of human-to-human transmission," he said. "The primary issue is to limit (that) human-to-human transmission."
The previously unknown coronavirus strain is believed to have emerged from an animal market in the central city of Wuhan, with cases now detected as far away as the United States.
Wuhan is closing its transport networks and advising citizens not to leave the city, state media reported on Thursday.
Australian Associated Press
