The head of the World Health Organization said on Tuesday he was "very disappointed" that China has still not authorised the entry of a team of international experts to examine the origins of the coronavirus.
The 10-strong team had been due to set off in early January as part of a long-awaited mission to probe early cases of the coronavirus, first reported over a year ago in China's Wuhan.
"Today we learned that Chinese officials have not yet finalised the necessary permissions for the team's arrival in China," WHO Director-General Tedros Adhanom Ghebreyesus told an online news conference in Geneva.
"I have been in contact with senior Chinese officials and I have once again made it clear the mission is a priority for the WHO," he said of the trip he said was developed with Beijing.
The mission was due to be led by Peter Ben Embarek, WHO's top expert on animal diseases that cross the species barrier, who went to China on a preliminary mission last July.
Two members of the international team had already set out on their journey to China. One has now turned back and the other is in transit in a third country, emergencies chief Mike Ryan said.
However, he added: "We trust and hope that is just a logistic and bureaucratic issue that can be resolved very quickly."
Ahead of the trip, Beijing has been seeking to shape the narrative about when and where the pandemic began, with senior diplomat Wang Yi saying "more and more studies" showed that it emerged in multiple regions. Ryan has previously called this "highly speculative".
China has dismissed criticism of its handling of early cases that emerged in late 2019, although some including US President Donald Trump has questioned Beijing's actions during the outbreak.
Washington, which has announced plans to leave the WHO, has called for a "transparent" investigation and criticised its terms under which Chinese experts conducted the first phase of research.