China cannot accept the World Health Organization's plan for the second phase of a study into the origins of Covid-19, a senior Chinese health official said Thursday.

Zeng Yixin, the vice minister of the National Health Commission, said he was “rather taken aback" by the call for a further probe into the pandemic's origins and, specifically, the theory that the virus might have leaked from a Chinese lab.

He dismissed the lab leak theory as a rumor that runs counter to common sense and science.

“It is impossible for us to accept such an origin-tracing plan,” he said a a news conference called to address the Covid-19 origins issue.

The search for the origins of the virus has become a diplomatic issue that has worsened China's relations with the U.S. and many of its allies.

The U.S. and others say that China has not been transparent about what happened in the early days of the pandemic. China accuses critics of politicizing an issue that should be left to scientists.

Tedros Adhanom Ghebreyesus, the director-general of the WHO, acknowledged last week that it was premature to rule out a potential link between the pandemic and a leak from a Chinese government lab in Wuhan, the city where the disease was first detected in late 2019.

Tedros said he hoped for better cooperation and access to data from China, adding that getting access to raw data had been a challenge for the international expert team that traveled to China this year to investigate the cause of the outbreak.

He also says there had been a “premature push” to rule out the theory that the coronavirus might have escaped from a Chinese government lab in Wuhan.

“I was a lab technician myself, I’m an immunologist, and I have worked in the lab, and lab accidents happen,” Tedros said.

Tedros' words were echoed by Germany’s health minister, Jens Spahn, who urged Chinese officials to allow the investigation into the origins of the virus to proceed.

Zeng said the Wuhan lab has no virus that can directly infect humans.