Russia’s diplomatic letter threatened “unpredictable consequences” if the US continues to arm Ukraine.
The letter, viewed by The Washington Post, also says the US is breaking international rules governing the transfer of weapons into conflict zones.
Russia accused NATO’s ongoing actions of impeding their peace negotiations with Ukraine “in order to continue the bloodshed”.
The State Department would not confirm or comment on private diplomatic correspondence, but a White House official who spoke to NBC News said the letter shows weapons deliveries are making a difference and that the White House is taking the note seriously.
The letter comes just after President Joe Biden announced an additional $800 million in military aide to Ukraine. It’s the first shipment which includes the advanced munitions requested by Ukrainian President Zelensky.
“The Ukrainian military has used the weapons we are providing to devastating effect. As Russia prepares to intensify its attack in the Donbas region, the United States will continue to provide Ukraine with the capabilities to defend itself,” Biden said at the time.