China on Wednesday criticised the US "politicisation" of efforts to trace the origin of the coronavirus, demanding without any evidence that American labs be investigated, ahead of the release of a US intelligence report on the virus.

The US report is intended to resolve disputes among intelligence agencies considering different theories about how the coronavirus emerged, including a once-dismissed theory about a Chinese laboratory accident.

"Scapegoating China cannot whitewash the US," Fu Cong, director-general of the Ministry of Foreign Affairs' arms control department, told a briefing.

US President Joe Biden received a copy and was briefed on the classified report on Tuesday, White House press secretary Jen Psaki told reporters on Wednesday.

The intelligence community has been "working expeditiously" to prepare an unclassified version for the public, Psaki said without giving a timeline for its release.

US officials say they do not expect the review to lead to firm conclusions after China stymied earlier international efforts to gather key information on the ground. 

China has said a laboratory leak was highly unlikely, and it has ridiculed a theory that coronavirus escaped from a lab in Wuhan, the city where Covid-19 infections emerged in late 2019, setting off the pandemic.

Beijing has instead suggested that the virus slipped out of a lab at the US Army's Fort Detrick base in Maryland in 2019.

"It is only fair that if the US insists that this is a valid hypothesis, they should do their turn and invite the investigation into their labs," Fu said.

Fu said China was not engaged in a disinformation campaign.

The fringe idea once put forward by individual Chinese officials - which lacks any public evidence - has become a Chinese government talking point as it attempts to deflect criticism about its possible role in the origins of the virus.

On Wednesday, the Chinese embassy in Washington posted the calls for World Health Organization investigations at Fort Detrick and at the University of North Carolina to its website after it said US media had rejected its editorial submissions.

And on Tuesday, China's envoy to the United Nations asked the head of the WHO for an investigation into US labs.

A joint WHO-Chinese team visited the Wuhan Institute of Virology but the United States said it had concerns about the access granted to the investigation.

"The early days of the pandemic were irrefutably in China, yet China continues to obfuscate and deny the international community the needed access," a senior US administration official said, adding that if a future pandemic were to originate in the United States, it would insist on a "swift and transparent" evaluation.

"If there were sound, technically credible reasons for a US investigation, we would of course support it. But there are none," said the official, who spoke on condition of anonymity.

Republican Senator Marco Rubio, who has argued a Chinese lab leak was plausible, in a statement urged the Biden administration to immediately declassify the report.

"The American people deserve to know what our government does and does not know about the origins of Covid-19," Rubio said.

A key Congressional panel has been advised it may receive a copy of the classified report on Thursday, according to a Congressional official.