President Joe Biden has ordered US intelligence officials to “redouble” their efforts to investigate the origins of the COVID-19 pandemic, including any possibility the trail might lead to a Chinese laboratory.

After months of minimising that possibility as a fringe theory, the Biden administration is joining worldwide pressure for China to be more open about the outbreak, aiming to head off GOP complaints the president has not been tough enough as well as to use the opportunity to press China on alleged obstruction.

Biden asked US intelligence agencies to report back within 90 days, and he told reporters on Thursday that he aimed to release their results publicly.

The Democrat directed US national laboratories to assist with the investigation and the intelligence community to prepare a list of specific queries for the Chinese government. He called on China to cooperate with international probes into the origins of the pandemic.

Republicans, including former president Donald Trump, have promoted the theory that the virus emerged from a laboratory accident rather than naturally through human contact with an infected animal in Wuhan, China.

Biden ordered an initial intelligence review in March and upon being presented with its conclusions determined more digging was required. He also ordered that excerpts of the assessment be declassified to demonstrate the US government’s commitment to investigating the origins of the pandemic and to increase pressure on China to cooperate, a source said.

Biden, in a statement, said the majority of the intelligence community had “coalesced” around those two scenarios but “do not believe there is sufficient information to assess one to be more likely than the other”.

He revealed that two agencies lean toward the animal link and “one leans more toward” the lab theory, “each with low or moderate confidence”.

“The United States will also keep working with like-minded partners around the world to press China to participate in a full, transparent, evidence-based international investigation and to provide access to all relevant data and evidence,” said Biden.

His statement came after weeks of the administration endeavouring to avoid public discussion of the lab leak theory and privately suggesting it was farfetched.

China on Thursday accused Biden’s administration of now playing politics and shirking its responsibility in calling for a renewed investigation into the origins of the coronavirus pandemic, which was first detected in China in late 2019.

Foreign Ministry spokesperson Zhao Lijian said Biden’s order showed the US “does not care about facts and truth, nor is it interested in serious scientific origin tracing”.

As for the origin of pandemic, Anthony Fauci, a White House coronavirus adviser, said Wednesday that he and most others in the scientific community “believe that the most likely scenario is that this was a natural occurrence, but no one knows that 100% for sure”.

“And since there’s a lot of concern, a lot of speculation and since no one absolutely knows that, I believe we do need the kind of investigation where there’s open transparency and all the information that’s available, to be made available, to scrutinise,” Fauci said at a Senate hearing.

White House press secretary Jen Psaki said Tuesday that the White House supports a new World Health Organisation investigation in China, but she added that an effective probe “would require China finally stepping up and allowing access needed to determine the origins.”

Biden still held out the possibility that a firm conclusion may never be reached, given the Chinese government’s refusal to fully cooperate with international investigations.

“The failure to get our inspectors on the ground in those early months will always hamper any investigation into the origin of Covid-19,” he said.

The Chinese Embassy in Washington, without mentioning the Biden order, accused unnamed political forces of being fixated on a blame game while ignoring the urgent need to combat the pandemic.

“Smear campaign and blame shifting are making a comeback, and the conspiracy theory of lab leak is resurfacing,” the embassy said in a statement posted on Wednesday on its website.

Administration officials continue to harbour strong doubts about the lab leak theory. Rather, they view China’s refusal to cooperate in the investigation — particularly on something of such magnitude — as emblematic of other irresponsible actions on the world stage.

Research into the origins of the virus is critically important, said Arinjay Banerjee, a virologist at the Vaccine and Infectious Disease Organisation in Saskatchewan, Canada, because, “if you don’t know where it came from, how are you going to stop it from spreading it again?”