- Putin said Russia would "respond accordingly" if the UK sends a "nuclear component" to Ukraine.
- The component: depleted uranium armor-piercing shells, which have no role in nuclear weaponry.
President Vladimir Putin said Russia would respond if the UK supplied Ukraine with armor-piercing shells containing depleted uranium.
"If all this happens, Russian will have to respond accordingly, given that the West collectively is already beginning to use weapons with a nuclear component," Putin said on Tuesday, according to Reuters.
On Monday, UK Defence Minister Annabel Goldie said in a parliamentary response that the UK will supply Ukraine with "armor piercing rounds which contain depleted uranium" alongside two Challenger-2 main battle tanks.
Depleted uranium, a by-product of the nuclear enrichment process, is used in making penetrating tank shells because it is extremely dense.
The Kremlin and pro-Russian figures seized on the UK's announcement with a flurry of aggrieved comments, saying it represents a form of escalation between Russia and the West, and that the rounds pose a health risk.
Russian Defense Minister Sergei Shoigu followed Putin's comments by saying that there were "fewer and fewer" steps before nuclear war with the West, the Telegraph reported.
And Russian foreign ministry spokesperson Maria Zakharova said that the UK was trying to provoke a "new round of aggression" with the move, suggesting that the announcement was planned in order to disrupt Putin's talks with Chinese President Xi Jinping.
Belarusian president Alexander Lukashenko, a Putin ally, echoed Putin's warning on Wednesday, according to TASS. "Russia has much more than just depleted uranium," he said, per the outlet.
But Russia upgraded some of its own tanks to use depleted-uranium munitions in 2018, which it said at the time didn't violate any international treaties.
The UK's Ministry of Defense said in a statement that Russia is "deliberately trying to disinform" over the matter.
"The British Army has used depleted uranium in its armour piercing shells for decades. It is a standard component and has nothing to do with nuclear weapons or capabilities," it said.
Weapons expert and former tank commander Hamish de Bretton-Gordon told The Telegraph that Putin's suggestion the munitions amount to nuclear escalation is "bonkers."
"Depleted uranium is completely inert," he told the newspaper. "There is no way that you could create a nuclear reaction or a nuclear explosion with depleted uranium."
The UK MOD also cited research that it says shows the health risk of depleted uranium munitions is "likely to be low."
Depleted uranium is much less radioactive than the original fuel. It's considered by the US EPA as a radiation health hazard when inside the body — thus potentially dangerous as shrapnel or dust — but does not emit enough radiation to penetrate the skin from outside.
Meanwhile, a 2010 EU public health assessment said that the use of depleted-uranium munitions has "raised concerns about health threats," but that studies on the question remain inconclusive.