An unusual public spat between two top Chinese diplomats points to an internal split in Beijing over how to handle rising tensions with a combative US president.

The differences spilled into public view yesterday after China's ambassador to the US reaffirmed his opposition to promoting theories that the virus that causes Covid-19 originated in an American military lab.

Ambassador Cui Tiankai said in an interview that he stood by his February 9 statement that it would be crazy to spread such theories, even though a foreign ministry spokesman has repeatedly floated the idea on Twitter in recent weeks.

"Such speculation will help nobody. It's very harmful," Cui said.

"Eventually, we must have an answer to where the virus originally came from. But this is the job for the scientists to do, not for diplomats."

Cui's comments represent a sharp public rebuke to foreign ministry spokesman Zhao Lijian, who has publicly questioned whether the virus originated in China and even touted the idea that it may have been introduced by US Army athletes. Such public differences are rare among Chinese officials.

The developments suggest that China's foreign ministry may be having second thoughts about taking a more confrontational approach toward President Donald Trump.

Another spokesman, Geng Shuang, told reporters "the virus should not be linked to a specific country or region to avoid stigmatization."

"Ambassador Cui is a professional and an adult. His comments should be taken as authoritative," said James Green, a senior adviser for geopolitical consulting firm McLarty Associates.

In recent weeks, Zhao has promoted theories that the coronavirus roiling the world was present in the US before the outbreak in China, a narrative that also circulated on state media.

Trump has taken to calling the pathogen the "Chinese virus" and has blamed the US outbreak on China's early failures to control the disease.

Cui Tiankai refuses to blame the US for the coronavirus pandemic. REUTERS

China envoys in virus feud