China rejected a plan for the second phase of an investigation into the origin of the coronavirus, which included a theory it could have escaped from a laboratory.
World Health Organisation studies would include audits of laboratories and markets in the city of Wuhan, where the first known cases emerged in December 2019.
"We will not accept such an origins-tracing plan as it, in some aspects, disregards common sense and defies science," Zeng Yixin, vice minister of the National Health Commission, said.
Mr Zeng said China opposed politicising the study of the virus, the origin of which is contested among experts.
In May, US President Joe Biden ordered aides to find answers to questions over the origin and said American intelligence agencies were pursuing rival theories including the possibility of a laboratory accident in China.
Mr Zeng, alongside officials and Chinese experts at a press conference, urged the WHO to expand origin-tracing efforts beyond China.
"We believe a lab leak is extremely unlikely and it is not necessary to invest more energy and efforts in this regard," said Liang Wannian, the Chinese team leader on the WHO joint expert team.
However, Mr Liang said the lab leak hypothesis could not be discounted entirely but suggested that if evidence warranted, other countries could look into the possibility it leaked from their labs.