A US expert warns of a potential agroterrorism threat after two Chinese scientists were charged with smuggling a toxic fungus into the US, suggesting it could lead to catastrophic consequences worse than Covid if relations with China aren't severed.

According to the FBI, Liu had small baggies of the fungus stashed in his backpack when he flew to the US last year. After claiming ignorance about the plant material inside them, he said he was planning to use them for research at a University of Michigan lab where Jian worked.

A top US-based expert on China has warned of "something worse" than Covid if the United States is not careful, days after two Chinese scientists were charged with allegedly smuggling a toxic fungus into the US.