While pressing China to allow a second novel coronavirus origin tracing investigation, the United States keeps babbling about "transparency" and "responsibility". But when it is the one being urged to allow a field study, its mouth remains sealed.

In the report it released in March on the more than four weeks of field research that a team of international experts carried out in Wuhan, Hubei province, the World Health Organization concluded that a lab leak was extremely unlikely to be the origin of the outbreak. The great lengths to which the US has gone to deny that conclusion, and its vow to replace the WHO in carrying out a phase two study in Wuhan, only lays bare the fact that the US has come to the end of its wits on how to deflect global attention from itself.

Phase two origin-tracing studies, as Zeng Yixin, vice-minister of the National Health Commission, made clear in a news conference on that topic in Beijing on Thursday, can only be carried out on the basis of the findings of the first-phase work, and this has not yet been completed. Field studies have yet to be conducted in the US and some other places where evidence has been uncovered that the virus was circulating before it was identified in Wuhan.

Any attempts to negate what the WHO did in its studies and pressure it to start the work all over again, not to mention to replace the WHO in the undertaking, goes against science, transparency and the principles the WHO has set for the research, and will necessarily guide the work astray.

So when White House press secretary Jen Psaki called China's rejection of another origin tracing study in Wuhan "irresponsible" and "dangerous", she was once again reeling out Washington's obviously fraying line blaming the pandemic on China.

When President Joe Biden ordered the US intelligence agencies to redouble their efforts to pin the blame on China in May and provide a report on the origins of the virus in 90 days, he stressed that the US, along with its allies, would press China to provide access to all relevant data and evidence, despite knowing that China has already done so. Like his predecessor, he feels no qualms about downgrading essential scientific work into a political witch-hunt.

It is predictable that his administration will go even farther in ignoring the common good just to smear China.

With the most deaths and infections caused by the virus, and so many questions remaining unanswered about the timeline of infections in the US, as well as a government that is trying to bolt the door on any origin tracing research on US soil, it is no wonder that there is growing suspicion that it is engaged in some kind of cover-up.