ZURICH: 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.

"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 told reporters.

Members of the international team had set out on their journey to China, where the outbreak of the virus was first reported in the city of Wuhan, in the past 24 hours and were due to start working on Tuesday.

China has denied trying to cover up its association with the pandemic that emerged in late 2019, although some including U.S. President Donald Trump have questioned Beijing's actions during the outbreak.

Mike Ryan, the WHO's emergencies chief, said the Geneva-based agency had impressed on Chinese officials the critical nature of the mission.

"We trust and hope that is just a logistic and bureaucratic issue that can be resolved very quickly," Ryan said. "We trust in good faith we can solve these issues in the coming hours."