WUHAN: US intelligence on the supposed origin of the coronavirus pandemic was not reliable, a member of the special WHO mission to China said Wednesday, after Washington cast doubt on the transparency of the probe.

The World Health Organization mission ended Tuesday without finding the source of the virus, but members had to walk a diplomatic tightrope during their stay, with the US urging a "robust" probe and China warning against politicising the issue.

Information dribbled out via their personal Twitter accounts during the mission, but more details and opinions emerged as they prepared to leave the country.

Peter Daszak, a member of the WHO team, waded directly into the murky geopolitics which covers the pandemic origin story.

President Joe Biden "has to look tough on China", he said in a tweet adding: "Please don't rely too much on US intel: increasingly disengaged under Trump & frankly wrong on many aspects."

Daszak also tweeted that they worked "flat out under the most politically charged environment possible".

His comments were linked to an article referencing US state department comments which cast doubt over the transparency of China's co-operation with the WHO mission.

State Department spokesman Ned Price said the White House "clearly support this investigation", but shared criticism that China concealed information.

Asked if China had fully cooperated with the WHO team, Price told reporters: "I think the jury's still out."