The US health secretary has urged the World Health Organization (WHO) to ensure the next phase of investigation into Covid-19's origins is "transparent".Speaking to a ministerial-level WHO meeting, Xavier Becerra said international experts should be allowed to evaluate the source of coronavirus.
US media reports suggest growing evidence the virus could have emerged from a laboratory in China.
Covid-19 was first detected in 2019 in Wuhan, in central Hubei province.
Since then, more than 167 million cases and 3.4 million deaths have been reported worldwide.
The WHO acknowledged further study was needed.