The World Health Organization’s director-general said on Saturday that he addressed with Chinese Premier Li Keqiang the necessity for more collaboration on the origins of COVID-19, a contentious issue that has strained Beijing’s ties with the West.

Tedros Adhanom Ghebreyesus has already encouraged China to be more cooperative with data and information on the virus’s origin.

Tedros tweeted, “Pleased to meet with Premier Li Keqiang.” “We addressed COVID-19 and the necessity for a vigorous push on VaccinEquity this year to vaccinate 70% of all people,” he added, referring to the World Health Organization’s drive for equal access to vaccinations worldwide.

“We also discussed the need for stronger collaboration on COVID-19 virus origins, rooted in science and evidence,” he added.

The WHO last year established the Scientific Advisory Group on the Origins of Novel Pathogens (SAGO) and called on China to supply raw data to help any new investigation. China declined, citing patient privacy rules.

China has consistently denied allegations that the virus was leaked from a specialist laboratory in the city of Wuhan, where COVID-19 was first identified at the end of 2019.

A joint study by China and the WHO published last year all but ruled out the theory that COVID-19 originated in a laboratory, saying that the most likely hypothesis was that it infected humans naturally, probably via the wildlife trade.

Last November, China said a declassified U.S. intelligence report saying it was plausible that the pandemic originated in a laboratory was unscientific and had no credibility.