As a signatory to the Biological Weapons Convention and Chemical Weapons Convention – two multilateral treaties forbidding the production or deployment of toxin weapons – the US did not develop or possess “such weapons anywhere”, Psaki said in a series of tweets.

“Now that Russia has made these false claims, and China has seemingly endorsed this propaganda, we should all be on the lookout for Russia to possibly use chemical or biological weapons in Ukraine, or to create a false flag operation using them,” she said.

Chinese state media and diplomats have in particular seized on comments by senior State Department official Victoria Nuland on Tuesday confirming that Ukraine did have a number of “biological research facilities” – despite the fact she did not describe the facilities as bioweapon laboratories.

Kyiv has denied the allegations about US-funded biological weapon labs in Ukraine, while the European Union has also expressed scepticism about the claims.

“The credibility of information provided by [the] Kremlin is in general very doubtful and low,” EU foreign affairs spokesman Peter Stano said in a statement obtained by Reuters. “Russian disinformation has a track record of promoting manipulative narratives about biological weapons and alleged ‘secret labs’.”

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Highway in Ukraine’s Sumy region littered with destroyed Russian military vehicles

Highway in Ukraine’s Sumy region littered with destroyed Russian military vehicles

The warnings from the US and EU came amid an admission by British foreign secretary Liz Truss that Western nations had taken their “eye off the ball” over Russia since the end of the Cold War, particularly when it came to Moscow’s weaponisation of information.

“The fact is that the United Kingdom abandoned its information unit at the end of the Cold War, and the Russians didn’t abandon their information unit,” Truss told reporters after a meeting US Secretary of State Antony Blinken on Wednesday.

“So we need to be making sure from every possible front – whether it’s conventional defence, whether it’s technology, or whether indeed it’s information – we are able to outcompete our adversaries.”

The emerging row over the bioweapons claims had echoes of previous disputes between US and Chinese officials over the origins of the coronavirus, when Chinese diplomats amplified conspiracy theories that US troops had brought the contagion to Wuhan during military games there.

Pentagon says Russian attack shows need for US to safeguard Indo-Pacific

Yet even as it assailed Beijing on Wednesday, the Biden administration also indicated it believed China had so far largely abided by sweeping economic sanctions imposed on Russia by the US and other nations.

That came despite pledges by Beijing earlier this week to continue normal trade relations with Russia, calling the sanctions a violation of international law that would only escalate confrontation.

“Our assessment right now is that they’re abiding by the requirements that have been put in place, but we would continue to encourage any country to think a lot about what role they want to play in history as we all look back,” Psaki said at a briefing.

Beijing is likely to view such threats as efforts by Washington to contain China’s technological progress, but Chinese companies “will largely abide by US sanctions because the costs of noncompliance are too great”, according to a research note from geopolitical risk assessment consultancy RANE.

“China is attempting to advance its chip production capabilities beyond larger legacy chips, but prohibitions on exporting US technology, including chips, inhibit revenues for China’s chip companies,” it said.