The US government said it is 'disappointed' by China's move.

"We have certainly seen the PRC’s comments again rejecting phase two of a WHO study.  We’re deeply disappointed.  Their position is irresponsible and, frankly, dangerous. 

"......we continue to call for China to provide the needed access to data and samples.  And this is critical so we can understand to prevent the next pandemic. This is about saving lives in the future.  And it’s not a time to be stonewalling,"  White House press secretary Jen Psaki said during a press conference on Saturday.

"I would note that we believe in a multilateral approach; that has not been an approach that has been taken prior to the President  taking office, and that has been a big focus of his strategy — strategy as it relates to our engagement with China," she said.

"So, and that relates to our approach to global health security, which is why we rejoined the WHO on day one.  Unfortunately, phase one, as you all know, did not yield the data and access from China that we think is necessary. But our support for a multilateral approach and the phase two plan is because it’s rigorous and science-based," she said.

Jen Psaki said: "It’s clear China isn’t living up to their obligations.  What our focus is on is building this multilateral effort and support for putting pressure on and making clear that it’s unacceptable and dangerous."

China is blamed by several nations for being the nation from which the COVID-19 virus emerged.