WASHINGTON (Reuters) -- US President Donald Trump on Tuesday urged China to be transparent about the origins of the novel coronavirus outbreak that has killed more than a quarter of a million people since it started in the Chinese city of Wuhan late last year.

Trump, speaking before leaving on a trip to Arizona, said the United States would release a report detailing the origins of the virus, but gave no details or timeline.

“We will be reporting very definitively over a period of time,” Trump told reporters.

While taking aim at China as the source of the outbreak and warning that it would be held to account, Trump and officials in his administration have expressed differing levels of confidence about the exact origin of the virus.

On Sunday, Secretary of State Mike Pompeo said there was “a significant amount of evidence” that it emerged from the Wuhan Institute of Virology, while not disputing US intelligence agencies’ conclusion that it was not man-made.

On Tuesday, General Mark Milley, the top US general, said it was still not known whether the coronavirus emerged from a wet market in China, the institute of virology or some other location -- echoing remarks Pompeo made last Thursday.

Trump was asked last Thursday if he had seen evidence that gave him a “high degree of confidence” that the virus came from the Wuhan Institute of Virology, and replied that he had, although he declined to give specifics.

The Chinese state-backed institute has dismissed allegations that the virus originated there. Most experts believe the virus originated in a Wuhan market selling wildlife and jumped from animals to people.

Trump, who initially praised China over its response to the outbreak, said he had not spoken to Chinese President Xi Jinping.

“We want them to be transparent. We want to find out what happened so it never happens again,” he said.

The Republican president, who is seeking re-election in November, has been accused of not acting early enough to curb the spread of the virus in the United States. He has said China should have warned the world much sooner.

Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases and a member of the White House Coronavirus Task Force, told National Geographic in an interview published on Monday the best evidence showed the virus was not made in a lab in China but appeared to have “evolved in nature and then jumped species.”

Asked if scientists could have found the virus outside the lab and brought it there, from where it escaped, Fauci said: “But that means it was in the wild to begin with. That’s why I don’t get what they’re talking about [and] why I don’t spend a lot of time going in on this circular argument.”

US Health Secretary Alex Azar was asked on Fox News about differences between Pompeo’s and Fauci’s remarks.

“I don’t think there’s a distinction between them. Of course, Secretary Pompeo has access to information that Dr. Fauci may not have, so there’s not necessarily a difference of opinion there,” he said on Tuesday.

The World Health Organization called the comments Pompeo made on Sunday “speculative.” Trump has halted US funding to the WHO and accused of it being “China-centric.” (Reuters)