US intelligence agencies have concluded that coronavirus was "not man-made or genetically modified" but say they are still examining whether the origins of the pandemic trace to contact with infected animals or an accident at a Chinese lab.

The statement from the Office of the Director of National Intelligence comes as President Donald Trump and his allies have touted the as-yet-unproven theory that an infectious disease lab in Wuhan, the epicentre of the Chinese outbreak, was the source of the global pandemic, which has killed more than 220,000 people worldwide.

In recent days the Trump administration has sharpened its rhetoric on China, accusing the nation of failing to act swiftly enough to sound the alarm to the world about the outbreak or to stop the spread of the virus that causes COVID-19.

"The IC 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."

Scientists around the world also examining the virus's point of origin say it arose naturally in bats. Even so, a number of leaders in the US have pointed fingers at an institute run by the Chinese Academy of Sciences.

In April, Mr Trump addressed the theory saying, "More and more, we're hearing the story."

Secretary of State Mike Pompeo added, "The mere fact that we don't know the answers — that China hasn't shared the answers — I think is very, very telling."

Mr Pompeo also pressed China to let outside experts into the lab "so that we can determine precisely where this virus began."

While Mr Trump and Mr Pompeo have made public statements speculating about the lab, a US intelligence official disputed the notion that there was any pressure on agencies to bolster a particular theory.

The intelligence official was not authorised to publicly discuss the issue and spoke only on condition of anonymity to the Associated Press

US officials say the American Embassy in Beijing flagged concerns about potential safety issues at the lab in Wuhan in 2018, but they have yet to find any evidence the virus originated there nearly two years later.

The Chinese Government has responded to the comments from US officials, saying any claims coronavirus was released from a laboratory are "unfounded and purely fabricated out of nothing."

Foreign Ministry spokesman Geng Shuang cited the institute's director, Yuan Zhiming, as saying the lab strictly implements bio-security procedures that would prevent the release of any pathogen.

"I would like to point out again that the origin of the virus is a complex scientific issue, and it should be studied by scientists and professionals," he said.

Mr Geng also criticised US politicians who have suggested China should be held accountable for the global pandemic, saying they should spend their time on "better controlling the epidemic situation at home."

ABC/ AP

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