The United States on Thursday questioned China's credibility on reporting fresh coronavirus cases in Beijing and called for neutral observers to assess the extent of the outbreak.

China has locked down the capital as it seeks to prevent a second wave of COVID-19, reporting 158 cases since a fresh cluster was detected last week.

Secretary of State Mike Pompeo, an outspoken critic of China, urged greater transparency during talks Wednesday in Hawaii with senior Chinese official Yang Jiechi.

"I would hope that their numbers and their reporting are more accurate than what we saw in the case of Wuhan and other places in the PRC, but that remains to be seen," said David Stilwell, the top US diplomat for East Asia who accompanied Pompeo.

"As far as numbers, it would be good to have folks on the ground to get confirmation" in Beijing, he told reporters.

Stilwell pointed to reports in scientific journals that gave higher estimates for COVID-19 cases in Wuhan, the metropolis where the global pandemic was first detected late last year.

"So once your credibility is lost, you will have to find a way to re-establish that," Stilwell said.

"I think the only way to do that is by bringing in neutral observers to help understand exactly what happened there."

The latest outbreak started in Beijing's sprawling Xinfadi wholesale market, which supplies more than 70 percent of the city's fresh produce.

After months of normality, Beijing has urged people not to leave the city and again closed schools.

Pompeo has been at the forefront of promoting a theory, discounted by mainstream scientists, that COVID-19 first emerged in a Wuhan laboratory.

China has accused President Donald Trump's administration of politicizing the pandemic to deflect from its own handling of the illness in the United States, which has suffered by far the highest death toll of any country.

AFP