Washington DC - FBI director Christopher Wray has confirmed an earlier assessment by the US domestic intelligence agency suggesting that the spread of the coronavirus "most likely" originated from a lab leak in China.

"The FBI has for quite some time now assessed that the origins of the pandemic are most likely a potential lab incident in Wuhan," where the virus first emerged in 2019, Wray told Fox News in an interview released on Tuesday evening.

Wray went on to say that the US agency assumed "a potential leak from a Chinese government controlled lab" was responsible for the global outbreak of the virus "that killed millions of Americans."

Investigations were still ongoing, the FBI director added, saying he was currently unable to share "a whole lot of details that are classified."

"I will just make the observation that the Chinese government, it seems to me, has been doing its best to try to thwart and obfuscate the work here," Wray said.

This was "unfortunate" for everyone, including the US government and its "close foreign partners."

US National Security Council communications director John Kirby had stressed on Monday that within the US government there was still no uniform view regarding the origins of the virus.

According to a Wall Street Journal report, the US Department of Energy is said to have changed its assessment of the origin of the virus and now assumes a possible laboratory incident could be responsible - but only with a "low" degree of certainty.

China has rejected the claims, with Beijing's foreign office spokesperson Mao Ning saying investigations into the origin of the virus were a scientific matter and should "not be politicized."