WASHINGTON, May 6, 2025 (BSS/AFP) - US President Donald Trump on Monday ordered new limitations on a form of biological research his administration says caused the Covid-19 pandemic through a lab leak in China.

The United States will halt funding in certain countries for so-called "gain-of-function" experiments -- aimed at enhancing the properties of pathogens -- according to an executive order Trump signed Monday at the White House.

"There's no laboratory that's immune from leaks -- and this is going to prevent inadvertent leaks from happening in the future and endangering humanity," Health Secretary Robert F. Kennedy Jr. wrote on X.

"Any nation that engages in this research endangers their own population, as well as the world, as we saw during the COVID pandemic," added Jay Bhattacharya, director of the National Institutes of Health.

Trump has long championed the theory that SARS-CoV-2 leaked from the Wuhan Institute of Virology as a result of gain-of-function research -- an alternative to the theory that the virus spilled over naturally from wild animals to humans at a seafood market in the same city.

The US government website Covid.gov, which previously focused on promoting vaccine and testing information, is now devoted to highlighting arguments that favor the lab leak.

Several US agencies, including the Federal Bureau of Investigation, the Department of Energy, and, most recently, the Central Intelligence Agency -- which shifted its stance under Trump's second term -- now lean toward a lab origin. Several other intelligence agencies favor natural spillover.

During the 2010s, the National Institutes of Health funded bat coronavirus research at the Wuhan Institute via the US-based nonprofit EcoHealth Alliance -- a grant axed by Trump in 2020 during his first term, but later partially restored under president Joe Biden.

Complicating matters, former top infectious disease official Anthony Fauci has maintained that the work in Wuhan did not meet the federal definition of gain-of-function, though some virologists and US officials have disputed that claim.

Trump's order names China as an example of a "country of concern" where such research should not be supported.

The order also seeks to end funding for other types of life sciences research in countries deemed to lack sufficient oversight, significantly broadening the types of foreign research that could be targeted.

It further calls for the development of a strategy to "govern, limit, and track dangerous gain-of-function research across the United States that occurs without federal funding" -- though the extent of the government's control over non-federal research is unclear, and the order also calls for new legislation to fill any gaps.

Trump's executive order comes amid broader efforts by his administration to reshape American science and health policy, including mass firings to government scientists and steep slashes to research budgets.