A report of Covid-19 origins by US intelligence agencies has not yielded a definitive conclusion on whether the new coronavirus jumped to humans naturally, or was the result of a lab leak, the media has reported.
US President Joe Biden had, in May, ordered the country's intelligence community "redouble their efforts" and report the origins of the pandemic within 90 days.
The new report, delivered to the White House on Tuesday highlights the challenge faced to get more information from China, the Wall Street Journal reported.
The lack of detailed information from China has affected the probe, two senior US officials were quoted as saying.
The report also underscores the importance of inducing China to share lab records, genomic samples, and other data that could provide further illumination on the origins of the virus, which has killed more than four million people world-wide, current and former officials said.
"It was a deep dive, but you can only go so deep as the situation allows. If China's not going to give access to certain data sets, you're never really going to know," one US official was quoted as saying.
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China has balked at the US and other efforts to provide that information. The extensive effort to press China for more information, some details of which haven't been previously reported, ended in bureaucratic infighting and failure, the WSJ report said.
While most of the new information gathered will likely remain classified, some will be released this week.
"It typically takes a couple of days, if not longer, to put together an unclassified version," Jen Psaki, the White House press secretary, said on Monday.
More than a year into the pandemic, the debate whether Covid-19s origins originated naturally or was leaked from a lab continues. A joint World Health Organization (WHO)-China inquiry, whose findings were released in March, dismissed as "extremely unlikely" the possibility that the virus had emerged accidentally from a laboratory.
Undermining its own report, director general Tedros Adhanom Ghebreyesus last month, proposed a second phase of studies in Wuhan. However, China has rejected the probe, accusing the WHO of "arrogance" and a "disrespect for common sense".
The US government's national laboratory had in a 2020 report on the origins of Covid-19 concluded that the virus leaked from a Chinese lab in Wuhan.
A recent investigation by the US House of Republican also revealed that the Covid-19 pandemic emerged from a genetically modified virus which leaked from the infamous Wuhan Institute of Virology (WIV).
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Meanwhile, China has dismissed the allegations, maintaining that the first cases likely emerged from animal to human transmission at a wet market in the city of Wuhan.
It has also dismissed the Wuhan lab leak theory as "extremely impossible" and has accused the US of "political manipulation".
Chinese scientists have asked the WHO to extend the hunt for origins of Covid-19 to labs in other countries including the US Army Medical Research Institute of Infectious Diseases (USAMRIID) at Fort Detrick, Maryland.