Donald Trump has publicly flirted with the unsubstantiated theory that the coronavirus was released from a Chinese laboratory "on purpose", as tensions between the two nations continue to rise.
Scientists have said the virus is most likely of natural origin, and spread from an infected animal to a human.
But The New York Times reports senior Trump administration officials, foremost among them Secretary of State Mike Pompeo, have been pushing intelligence agencies to find evidence supporting the theory – again, so far unsubstantiated – that the virus originated in a Wuhan research lab.
Speaking at the White House today, the President claimed to have seen evidence backing up the theory.
"We have people looking at it very, very strongly. Scientific people, intelligence people and others. We're going to put it all together. I think we will have a very good answer. And China might even tell us," Trump told reporters.
Asked to explain what evidence he had seen, he demurred.
"I can't tell you that. I'm not allowed to tell you that," he said.
Trump also floated the even more dramatic theory that China released the virus on purpose.
"It's a terrible thing that happened," the President said.
"Whether they made a mistake, or whether it started off as a mistake and then they made another one, or did somebody do something on purpose?" he mused.
"Certainly it could have been stopped. They either couldn't do it from a competence standpoint, or they let it spread."
In a statement, America's Director of National Intelligence confirmed the lab accident scenario was still being considered as a possibility, but ruled out the idea that the virus was a man-made bioweapon.
"The intelligence community concurs with the wide scientific consensus that the COVID-19 virus was not man-made or genetically modified," he said.
"The intelligence community will continue to rigorously examine emerging information and intelligence to determine whether the outbreak began through contact with infected animals or if it was the result of an accident at a laboratory in Wuhan."
China, for its part, has said the lab theory is "purely fabricated out of nothing".
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Today's news comes amid reports the US is drawing up plans to punish China for its handling of the pandemic.
In an interview with Reuters in the Oval Office yesterday, Trump said he was considering a range of options for imposing consequences on China, which has been accused of trying to cover up the outbreak when it first emerged in Wuhan.
That, he said, robbed other countries of precious time they could have used to prepare for the virus.
Last month, US intelligence agencies concluded China was still providing the rest of the world with an inaccurate number of cases and deaths.
"I can do a lot," Trump told Reuters.
"There are many things I can do. We're looking for what happened."
Trump repeatedly praised Chinese President Xi Jinping during the early months of the pandemic, thanking Mr Xi for his "transparency" and saying he had handled the crisis "really well".
But that has changed in recent weeks. Facing sustained criticism of his own coronavirus response, which critics say was far too slow, Mr Trump has sought to deflect the blame onto China.
"There are a lot of ways you can hold them accountable," he said at a coronavirus briefing earlier this week.
"We're doing very serious investigations, as you probably know. And we are not happy with China. We are not happy with that whole situation. Because we believe it could have been stopped at the source.
"It could have been stopped quickly, and it wouldn't have spread all over the world."
During the interview with Reuters, he suggested China was trying to damage his chances of winning re-election.
"China will do anything they can to have me lose this race," Mr Trump said.
In its own statement today, China told the United States to focus on its own problems.
"China, like the US, is a victim of the virus," said Foreign Ministry spokesman Geng Shuang.
"At this particular time they should focus on domestic epidemic control and international anti-epidemic co-operation, rather than attack, smear or shift blame onto China."
The Chinese government's state-run media mouthpieces have been even less diplomatic. In recent days, they have aired and published particularly scathing assessments of Pompeo, who has been the most persistent official voice promoting the lab theory.
On Monday, The People's Daily labelled Pompeo "poisonous", saying he had shown his "most twisted and ferocious face" by "fabricating rumours" against China.
One TV news anchor, Hai Xia called him an "enemy of humankind". Another, Ouyang Xiadan, accused him of using "lying, cheating, stealing tricks".
The People's Daily targeted Pompeo twice more throughout the week, branding him a "bully".
And the Xinhua news agency rounded things off with this animation.
Trump is under immense political pressure back home, where the virus continues to kill about 2000 Americans per day. Yesterday the death toll passed 60,000.
Less than a fortnight ago, Trump had predicted the total number of deaths in the US could top out at that number.
"It looks like we'll be at about a 60,000 mark, which is 40,000 less than the lowest number thought of," Trump said on April 19.
The "lowest number" he was referring to came from the previous White House forecast of 100,000-240,000 deaths.
"The low number was supposed to be 100,000 people. We could end up at 50 to 60," he added at the next day's briefing.
The President was seizing on modelling published by the University of Washington's Institute for Health Metrics and Evaluation, which projected as few as 60,000 deaths in the first wave of the pandemic. It expected that wave to last until August.
Instead, the US has reached that mark before the end of April – three months ahead of schedule.
Trump's focus has turned towards starting to reopen America's economy.
Today marked the end of the federal government's guidelines for "slowing the spread" of the virus, which included social distancing rules. They have been replaced by new guidelines, designed to tell state governors how to reopen their economies "safely and responsibly".