GENEVA: A top World Health Organization official on Friday criticised the fractious debate that has recently arisen between the US and China regarding the ongoing search for the origins of the COVID-19 pandemic, saying that the whole process had been "poisoned by politics".

Speaking in Geneva, WHO emergencies chief Dr. Michael Ryan said it would likely take "multiple studies and multiple trips" to determine the original source of the coronavirus and allowed that the complexity of the task suggested that might not even be possible.

Ryan said the claims in recent days over where the virus may have originated - fueled by US President Joe Biden's order this week that US intelligence agencies renew their efforts into probing COVID-19's source - were largely without evidence.

"If you expect scientists to collaborate and actually get the answers that you want...we would ask that all this be done in a de-politicised environment, where science and health is the objective, and not blame and politics," Ryan said.

He added that all hypotheses as to how the pandemic began remained "on the table".

In a report issued in March, a WHO-led international team concluded that the most likely explanation for the pandemic was that the virus jumped into humans from bats, via an intermediary animal.

WHO judged the likelihood of the outbreak starting in a laboratory as "extremely unlikely".