Russia has said its troops could target supplies of Western weapons in Ukraine, where the Russian army has been advancing since late February.
“We warned the United States that the orchestrated pumping of weapons from a number of countries is not just a dangerous move, it is a move that turns these convoys into legitimate targets,” Russian Deputy Foreign Minister Sergei Ryabkov told state television on Saturday.
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He said Moscow had warned “about the consequences of the thoughtless transfer to Ukraine of weapons like man-portable air defence systems, anti-tank missile systems and so on”.
Ryabkov said Washington had not taken Moscow’s warnings seriously and added that Russia and the United States were not holding any “negotiation processes” on Ukraine.
President Vladimir Putin sent Russian troops into Ukraine on February 24 and said he aims to “de-Nazify” the country.
Moscow has been hit by a barrage of international sanctions since Putin sent in troops.
Ukraine President Volodymyr Zelenskyy has repeatedly called on Western powers to deliver more military aid to his country, warning that Russia’s military will not stop at Ukraine’s borders if Moscow seizes full control.
While the US and NATO have rejected Zelenskyy’s repeated calls to implement a no-fly zone over Ukraine, they are shipping weapons into Ukraine at breakneck speed, including highly sensitive items such as shoulder-fired missiles called man-portable air defence systems (MANPADS) that can take down aircraft.
The Western arms deliveries have been vital to enabling Ukrainians to fight the invading Russian forces far more effectively and fiercely than US intelligence expected.
The US Senate on Thursday approved $6.5bn for military assistance for Ukraine.
For the first time in its history, the European Union is financing the purchase and delivery of arms after leaders agreed to transport weapons worth 450 million euros ($502m) to Kyiv.
Two days after the invasion of Ukraine by Russia began, Berlin said it will supply 1,000 anti-tank weapons and 500 Stinger missiles, in a U-turn from its policy of banning weapon exports to conflict zones.
In a similar change of policy, the Norwegian government also said in late February it is donating up to 2,000 M72 anti-tank weapons.
On Saturday, Ukrainian civilian fighters and residents in the capital prepared for a major attack as Russian forces surrounded the city with troops and artillery just kilometres away.
Fighting raged northwest of Kyiv, with the bulk of Russian ground forces 25km (16 miles) from the centre of the Ukrainian capital.