“Either it was an act of negligence or corruption. It wasn’t a failure. It was a betrayal.”
The commander also showed the BBC drone footage of Russian troops walking across the border.
Ukraine’s military chief, Oleksandr Syrskyi, has admitted that Kyiv’s soldiers are in a “difficult situation.”
He said: “Units of the defence forces are fighting fierce defensive battles, the attempts of the Russian invaders to break through our defences have been stopped.
“The situation is difficult, but the defence forces of Ukraine are doing everything to hold defensive lines and positions, (and) inflict damage on the enemy.”
This comes as Russia reportedly takes control of nine villages near Kharkiv.
Speaking last week, Ukrainian President Volodymyr Zelensky vowed that Ukraine will fend off the Russian assault.
He told reporters: “Russia launched a new wave of counter-offensive actions in this area. Ukraine met them there with our troops, brigades, and artillery … Now there is a fierce battle underway.
“Along our state border and along our front line, we will invariably destroy the occupier in such a way as to thwart any Russian offensive intentions.”
US National Security Council spokesman, John Kirby, added: “It is possible that Russia will make further advances in the coming weeks, but we do not anticipate any major breakthroughs, and over time, the influx of US assistance will enable Ukraine to withstand these attacks over the course of 2024.
“Russia will likely increase the intensity of fire and commit additional troops in an attempt to establish a shallow buffer zone along the Ukrainian border.
“We are confident in the Ukrainian (forces) and we are working around the clock to get them the equipment, the tools, the weapons that they need to defend against these attacks.”
