Russian President Vladimir Putin warns that Moscow will react to an earlier decision by the UK to arm Ukraine with ammunition containing depleted uranium.
Speaking in London on Monday, Britain's Minister of State for Defense Annabel Goldie said some of the ammunition for the Challenger 2 battle tanks that Britain was sending to Ukraine included armor-piercing rounds, which contain depleted uranium.
"The United Kingdom...announced not only the supply of tanks to Ukraine, but also shells with depleted uranium. If this happens, Russia will be forced to react," Putin told reporters in Moscow on Tuesday.
Russian Defense Minister Sergei Shoigu also cautioned that the British decision was moving Moscow and the West closer to the brink of "nuclear collision."
"Another step has been taken, and there are fewer and fewer left," he told reporters in remarks cited by domestic agencies.
Ammunition containing depleted uranium can pierce tanks and similar armor-plated vehicles due to the nuclear component's density and other physical properties.
"Naturally, Russia has something to answer this with," Shoigu added.
Russia started a military campaign in neighboring Ukraine last February to defend the pro-Russian population in the eastern Ukrainian regions of Donetsk and Luhansk against persecution by Kiev.
Ever since the beginning of the war, Western countries, led by the United States, have been slapping Russia with a slew of economic sanctions and pumping Ukraine full of advanced weapons, steps that Moscow says would only prolong the hostilities.
The West's ongoing armament of Ukraine comes, although, Putin recently said he welcomed a Chinese proposal for mediation between Moscow and Kiev towards resolution of the now-year-long conflict.