China accused the U.S. of attempting to smear the country after a Sunday report from the U.S. Department of Energy found that COVID-19 most likely leaked from a lab.

Reporters pressed Chinese Foreign Ministry spokeswoman Mao Ning about the report during a Monday briefing. Mao dismissed the report, however, citing the much-criticized joint WHO-China investigation into the origins of the virus.

"The origins-tracing of SARS-CoV-2 is about science and should not be politicized. China has always supported and participated in global science-based origins-tracing," Mao said Monday. "'A laboratory origin of the pandemic was considered to be extremely unlikely' is a science-based, authoritative conclusion reached by the experts of the WHO-China joint mission after field trips to the lab in Wuhan and in-depth communication with researchers. It was accurately recorded in the mission’s report and has received extensive recognition from the international community."

"Certain parties should stop rehashing the "lab leak" narrative, stop smearing China and stop politicizing origins-tracing," Mao continued.

LANCET CALLS FOR ‘OBJECTIVE, OPEN AND TRANSPARENT’ DEBATE OVER COVID-19 ORIGINS

China's dismissal comes one day after the U.S. Department of Energy joined the FBI in finding that an accidental lab leak was the most likely source of the COVID-19 outbreak, though it made the assessment with "low confidence."

In a statement to Fox News Digital on Sunday, a spokesperson for the Energy Department said, "The Department of Energy continues to support the thorough, careful, and objective work of our intelligence professionals in investigating the origins of COVID-19, as the President directed.

ANOTHER US AGENCY ASSESSES COVID-19 ORIGIN LIKELY A CHINESE ‘LAB LEAK’: REPORT

National Security Advisor Jake Sullivan was asked about the Journal’s report during an appearance on CNN Sunday: "There is a variety of views in the intelligence community. Some elements in the intelligence community have reached conclusions on one side, some on the other. A number of them have said they just don’t have enough information to be sure," Sullivan said.

The Sunday triggered a slew of frustrated responses from Republicans, whose questions about the origins of COVID-19 and the lab leak theory were long dismissed as conspiracies.

"Re. China’s lab leak, being proven right doesn’t matter," Sen. Tom Cotton, R-Ark., tweeted. "What matters is holding the Chinese Communist Party accountable so this doesn’t happen again."

Both the Washington Post and the New York Times had accused Cotton of repeating a "fringe theory" when he mentioned the lab leak possibility back in February 2020. The Post issued a correction to one of its stories more than a year after calling the theory "debunked."

Republicans are likely to renew focus on COVID-19's origins now that they control the House of Representatives and the committees that come with it.

Fox News' Jessica Chasmar and Danielle Wallace contributed to this report.