Members of an international expert team set off for China to investigate the origins of the Covid-19 pandemic, but Beijing has yet to grant them entry, the WHO chief said Tuesday.
"Today, we learned that Chinese officials have not yet finalised the necessary permissions for the team's arrivals in China," Tedros Adhanom Ghebreyesus told reporters.
"I am very disappointed with this news, given that two members had already begun their journeys and others were not able to travel at the last minute," he said, in a rare rebuke of Beijing from the UN body.
He stressed that he had been in contact with senior Chinese officials to make clear "that the mission is a priority for WHO and the international team."
"I have been assured that China is speeding up the internal procedure for the earliest possible deployment."
The World Health Organization's emergencies director Michael Ryan told Tuesday's briefing that the problem was a lack of visa clearances.
"We trust and we hope that this is just a logistic and bureaucratic issue that can be resolved very quickly."
The WHO has for months been working to send a 10-person team of international experts, including epidemiologists and animal health specialists, to China to help probe the animal origin of the novel coronavirus pandemic and how the virus first crossed over to humans.
But the mission is sensitive, and neither the WHO nor China had until now confirmed when specifically it was due to start, with the UN health agency only hinting it would take place during the first week of January.
- 'Critical' mission -
Ryan stressed that the WHO had been "working on close planning with colleagues in China and other countries for the dispatch of the team."
"We were all operating on the on the understanding that the team would begin deployment today," he said, adding that two members of the team coming from far away had set off early Tuesday, before it became clear that the necessary approvals had not been received.
"We trust that in good faith, we can solve these issues in the coming hours and recommence the deployment of the team as urgently as possible," Ryan said.
He stressed the "absolute critical nature" of the mission, acknowledging that the situation was "frustrating and... disappointing."
Covid-19 was first detected in the central city of Wuhan in late 2019, before seeping beyond China's borders to wreak havoc, costing over 1.8 million lives and eviscerating economies.
But its origins remain bitterly contested, lost in a fog of recriminations and conjecture from the international community -- as well as obfuscation from Chinese authorities determined to keep control of the virus narrative.
Scientists initially believed the killer virus jumped to humans at a market selling exotic animals for meat in the city of Wuhan, where the virus was first detected late last year.
But experts now think the market may not have been the origin of the outbreak, but rather a place where it was amplified.
It is widely assumed that the virus originally came from bats, but the intermediate animal host that transmitted it between bats and humans remains unknown.