The provision of anti-personnel land mines is the latest move by the outgoing US administration to bolster Ukraine’s war effort before Donald Trump returns to the White House on 20 January.
Russia has deployed landmines liberally since the start of its full-scale invasion of Ukraine in February 2022 but international objections to the use of such weapons on the grounds that they pose a risk to civilians had prevented the Biden administration from signing off on them.
The US defence official confirmed to the BBC that Ukraine had pledged to use only mines that remained active for a limited period of time.
The US “non-persistent” mines differ from Russia’s as they become inert after a pre-set period of time – anywhere from four hours to two weeks. They are electrically fused and require battery power to detonate. Once the battery runs out, they will not detonate.
Washington has already been providing anti-tank mines to Ukraine, but the anti-personnel land mines – which can be rapidly deployed – are designed to blunt the advances of ground forces.
Earlier, it was confirmed that US-made longer-range Army Tactical Missile System (Atacms) missiles had struck targets inside Russia only days after reports emerged that the White House had granted permission for their use.
Russia’s defence ministry said the strike had targeted the Bryansk region bordering Ukraine to the north on Tuesday morning.
It said five missiles had been shot down and one had caused damage – with its fragments starting a fire at a military facility.
But two US officials said initial indications suggested Russia had intercepted just two missiles out of around eight fired by Ukraine.
The BBC has not been able to verify independently the contradicting figures.
Russian Foreign Minister Sergei Lavrov accused Washington of trying to escalate the conflict.
The Kremlin has vowed to retaliate.