He confirmed that Taiwan has signed up to the scheme, even though it is not a WHO member, bringing the total to 159 participants. Some 34 are still deciding.

Talks with China also include discussion of the world's second-largest economy potentially supplying vaccines to the scheme, he said.

The UN agency published on Friday draft criteria for the assessment of emergency use of COVID-19 vaccines to help guide drugmakers as vaccine trials reach advanced stages, said WHO assistant director-general, Mariangela Simao.

The document will be available for public comment until Oct. 8, she said.

Earlier on Friday, a Chinese health official said the WHO had given its support for the country to start administering experimental coronavirus vaccines to people even while clinical trials were still underway.