The WHO on Friday urged all countries to reveal what they know about the origins of Covid-19, following US claims of a Chinese lab leak and furious denials from Beijing.
FBI Director Christopher Wray told Fox News television on Tuesday that the US Federal Bureau of Investigation had now assessed the source of Covid-19 pandemic was "most likely a potential lab incident in Wuhan".
Chinese officials have angrily denied the claim, calling it a smear campaign against Beijing.
"If any country has information about the origins of the pandemic, it's essential for that information to be shared with WHO and the international scientific community," the World Health Organization's director-general Tedros Adhanom Ghebreyesus insisted.
"Not so as to apportion blame but to advance our understanding of how this pandemic started so we can prevent, prepare for and respond to future epidemics and pandemics," he told a press conference.
"WHO has not abandoned any plans to identify the origins of the Covid-19 pandemic," he stressed.
In 2021, the United Nations' health agency set up the so-called Scientific Advisory Group for the Origins of Novel Pathogens, which identified key studies that are needed in China and elsewhere to test hypotheses on the origins of the pandemic.
- WHO urges transparency -
"WHO continues to call for China to be transparent in sharing data and to conduct the necessary investigations and share the results," said Tedros, adding that he had written and spoken to top Chinese leaders on multiple occasions.
"Until then, all hypotheses on the origins of the virus remain on the table," he said.
But he added that continued politicisation of the origins research was turning a purely scientific process into a geopolitical football, making the task harder -- and thereby the world less safe.
The first infections were recorded in the Chinese city of Wuhan in late 2019.
Wray's comments come after a report earlier this week said the US Department of Energy had determined that a leak from a Chinese lab was the most likely cause of the Covid-19 outbreak.
The department works with a network of national laboratories, including some that do advanced biological research. Other agencies within the US intelligence community believe the virus emerged naturally.