The US intelligence community does not believe it can resolve a debate over whether a Chinese laboratory incident was the source of Covid-19 without more information, officials said in a declassified summary on Friday.
The report, issued by the Office of the Director of National Intelligence in response to President Joe Biden's request for an investigation, said a satisfying answer remains out of reach to the question of how exactly a virus that has killed 4.6 million people worldwide started.
"China's cooperation most likely would be needed to reach a conclusive assessment of the origins of Covid-19," they said.
Biden, who received a classified report earlier this week summarising the investigation, said Washington and its allies will continue to press the Chinese government for answers.
"Critical information about the origins of this pandemic exists in the People's Republic of China, yet from the beginning, government officials in China have worked to prevent international investigators and members of the global public health community from accessing it," Biden said in a statement.
The summary, released by the Office of the Director of National Intelligence, was set to worsen discord between Beijing and Washington at a time when the countries' ties are at their lowest point in decades. In the United States, activists worried the investigation could also encourage violence against Asian Americans.
China has ridiculed a theory that Covid-19 escaped from the state virology lab in Wuhan and pushed fringe theories including that the virus slipped out of a lab in Fort Detrick, Maryland, in 2019.
The US report revealed new detail about the extent of the disagreement within the Biden administration over the so-called lab leak theory.
Several organisations within the sprawling US intelligence community thought the novel coronavirus emerged from "natural exposure to an animal infected with it or a close progenitor virus", according to the summary.
But they had only "low confidence" in that conclusion, the summary said. Other groups were not able to come to any firm opinion at all on the origins.
One intelligence community segment, however, developed "moderate confidence" that the first human infection with Covid-19 was likely due to a "laboratory-associated incident, probably involving experimentation, animal handling, or sampling by the Wuhan Institute of Virology" in China.
A team led by the World Health Organisation (WHO) that spent four weeks in and around Wuhan in January and February dismissed that theory. But their March report which was written jointly with Chinese scientists, has been faulted for using insufficient evidence to dismiss the theory.
The new US report concluded that analysts would not be able to provide "a more definitive explanation" without new information from China, such as clinical samples and epidemiological data about the earliest cases.
Initially, US spy agencies strongly favoured the explanation that the virus originated in nature. But people familiar with intelligence reporting have said there has been little corroboration over recent months that the virus had spread widely and naturally among wild animals.
"While this review has concluded, our efforts to understand the origins of this pandemic will not rest," Biden said. "We will do everything we can to trace the roots of this outbreak that has caused so much pain and death around the world, so that we can take every necessary precaution to prevent it from happening again."
The World Health Organisation's director-general, Tedros Adhanom Ghebreyesus, has said the group has not ruled out any hypothesis. The Geneva-based organisation is set to form a new committee to develop next steps on studying the virus SARS-CoV-2.
But epidemiological experts said the window was closing for any useful data to be collected, particularly from people infected by the disease in 2019, when the virus likely first emerged.
- Reuters