In a series of tweets Thursday and Friday, Zhao Lijian promoted the theory, without evidence, that the U.S. military is responsible for the pandemic by bringing it to China last October, giving new fodder for a narrative that's churned on the Chinese internet.
Altogether, it's a sign of not just the tensions between the two world powers, but also the growing battle over information in the 21st century -- with Russian disinformation efforts also spreading conspiracy theories about an alleged U.S. role, according to U.S. officials.
For China, the intentional spread of disinformation about the outbreak is as much about casting its response as superior to America's as it is about defending its reputation at home, where the Chinese public has expressed strong dissatisfaction online with the government's slow, opaque response -- including an effort to crack down on whistleblowers in the early days of the outbreak.
"There is a social media propaganda campaign on WeChat and other social media platforms in China to blame the West, to blame the CIA, and there is a very deliberate propaganda line from the Chinese government that their response to the virus demonstrates that Chinese governance is superior to the West," said Michael Green, senior vice president for Asia at the Center for Strategic and International Studies, a Washington think tank.
In particular, Zhao took to Twitter, which the government blocks for the Chinese public, to share an article from a fringe conspiracy site titled, "Further Evidence that the Virus Originated in the U.S."
A day earlier, he tweeted more directly, "It might be US army who brought the epidemic to Wuhan. Be transparent! Make public your data! US owe us an explanation!"
China's ambassador to the U.S. was summoned to the State Department Friday to protest his comments, a State Department official told ABC News. The top U.S. diplomat for Asia, Assistant Secretary David Stilwell gave Ambassador Cui Tiankai a "very stern representation of the facts," and Cui was "very defensive," the official added.
"China is seeking to deflect criticism for its role in 'starting a global pandemic and not telling the world.' Spreading conspiracy theories is dangerous and ridiculous," the official said. "We wanted to put the government on notice we won’t tolerate it for the good of the Chinese people and the world."
As part of the World Military Games, a U.S. military delegation, with 17 teams and 280 players and staffers, visited Wuhan in October, but there's no evidence they carried with them this coronavirus. Instead, all available evidence suggests the virus at least emanated from the Wuhan area, in Hubei province, China.
Scientists have not yet identified a "patient zero," but the first cluster of patients was reported at a seafood market in Wuhan, spreading rapidly after that. But in the early days, Chinese officials downplayed the risk publicly, while arresting several doctors who reported cases to higher authorities and initially declining to meet with U.S. medical officials after the U.S. Centers for Disease Control and Prevention and National Institutes of Health offered help.
Now, the Trump administration has ramped up its public diplomacy to combat questions about the origins. On two occasions, Pompeo has addressed reporters in part to chastise the Chinese government's response, calling it slow and marred by censorship.
"It can have deadly consequences. Had China permitted its own and foreign journalists and medical personnel to speak and investigate freely, Chinese officials and other nations would have been far better prepared to address the challenge," he said on Feb. 25, prompting calls for an apology and accusations he was "politicizing" the outbreak by China's Foreign Ministry.
Despite Trump's more conciliatory tone and praise for Chinese President Xi Jinping, Pompeo doubled down, telling CNBC last Friday, "This is the Wuhan coronavirus that's caused this, and the information that we got at the front end of this thing wasn't perfect and has led us now to a place where much of the challenge we face today has put us behind the curve."
Zhao's tweets don't dispute that the outbreak ultimately emanated from Wuhan into a pandemic -- just that it started there with a Chinese citizen. But his attacks seem like an escalation in the face of U.S. criticism, spiraling into a diplomatic tit-for-tat.
That's come particularly as the outbreak has lessened in China, with just five new cases reported in Wuhan on Thursday. President Jinping visited the city Wednesday in what was something of a victory lap for China's aggressive tactics to clamp down on the virus's spread, although there were reports that he and other top Communist Party officials were booed.
At a briefing Friday, another Foreign Ministry spokesperson -- Geng Shuang -- was more diplomatic.
"There are different opinions in the U.S. and among the larger international community on the origin of the coronavirus," he said. "China believes it's a matter of science which requires professional and science-based assessment."
Beyond Beijing, Russia has also been involved in spreading disinformation about the U.S. creating or spreading the coronavirus outbreak, according to U.S. officials.
The State Department's Global Engagement Center, which tracks and counters terrorist propaganda and foreign government disinformation, reported last week that "the entire ecosystem of Russian disinformation has been engaged in the midst of this world health crisis," according to its director, Lea Gabrielle.
"It includes Russian state funded media, official accounts, proxy news sites that spin conspiracy theories under the guise of journalism and then legions of false social media personas -- many of those were not bots," she told the Senate, while declining to detail the false information in order to not spread it further. "But we saw thousands pushing out false information."
ABC News's Karson Yiu contributed to this report from Hong Kong and Mel Madarang from Washington.