FOOTAGE appears to show Ukraine unleashing a US-supplied missile into Russia for the first time.
Kyiv blitzed a military depot on Russian turf just days after Joe Biden gave his blessing for far-reaching ATACMS rockets to be used.
The outgoing president's decision sparked fury in the Kremlin - with enraged Vladimir Putin drastically ramping down Moscow's threshold for Russia's use of nuclear weapons in retaliation.
Now footage has emerged that appears to show Ukraine launching an ATACMS missile from an undisclosed location.
The short clip - posted by a Telegram channel affiliated with the Ukrainian military - shows a huge plume of smoke trailing behind a flaming missile as it shoots high into the air.
Moscow was forced to admit yesterday on the 1,000th day of Vlad's illegal war that a US-supplied missile had hit an ammo arsenal in Bryasnk.
Fragments of one of the damaged rockets landed on the "technical territory" of the military facility and sparked a fire, Russia's defence ministry begrudgingly conceded.
Kyiv later confirmed that the warehouse they struck was storing North Korean ammunition and anti-aircraft missiles, via official Andriy Kovalenko on Telegram.
Moscow warned it would "react accordingly" if US-supplied weapons were used to strike Russian territory.
Now the US embassy in Kyiv has shut as Ukraine braces for a huge Russian revenge attack.
The US embassy said it has received "specific" intel about a "potential significant air attack".
It said: "Out of an abundance of caution, the embassy will be closed, and embassy employees are being instructed to shelter in place."
Kyiv braces for huge strike after Ukraine blitzes deep in Russia for 1st time
In an unusual warning, the embassy told US citizens to "be prepared to immediately shelter in the event an air alert is announced".
The UK government is also watching the security situation for Brits in Kyiv "incredibly closely" - but the embassy in the capital remains open.
Putin has repeatedly warned that Moscow will respond to Ukraine's strikes with US-made weapons deep into Russia.
In September, he said it would "mean that Nato countries are at war with Russia".
And just days after the US approved Ukrainian use of its far-reaching rockets, Vlad signed a new doctrine to lower the bar for launching a nuclear strike.
But sources have today claimed Putin is ready to discuss a Ukraine ceasefire deal with Donald Trump.
Vlad is, however, understood to have a list of heavy demands - including Kyiv abandoning its plan to join Nato.
How Ukraine could turn war around in WEEKS using US missiles
By Sayan Bose, Foreign News Reporter
Putin's forces invaded their neighbouring nation in February 2022 as part of the deluded tyrant's plan to rebuild the Soviet Union amid his paranoid fears over Nato.
Almost three years later, Kyiv's battle-weary troops are fighting to the death on multiple fronts.
They have faced several setbacks in the grinding conflict as Russia has made slow but incremental gains over Ukrainian territory.
But the green light from the US that now allows Ukraine to use long-range ATACMS missiles could be a game changer, an expert has said.
Colonel Hamish de Bretton-Gordon told The Sun how Ukraine could turn the war around in six weeks when provided with unwavering support from key allies in the West.
The former British army officer said Washington's decision to allow Ukraine to use ATACMS - and the prospect of Britain's Storm Shadow missiles joining the war effort - is a "significant development".
He explained: "Since day one Putin and his close aides have been threatening a nuclear strike if we escalate it, and today is the 1,000th day of this conflict, and it hasn't happened.
"It should embolden our leaders, who must now realise that Putin's threats are completely hollow.
"With the Russian boxer on the ropes, now is the time that we enable the Ukrainians to absolutely put in the killer punch and be in a really good position for the expected ceasefire."
He added: "The fact that the Russians have been so vehement in their verbal attacks against the use of Nato missiles shows that this is a significant step.
"It could allow Ukraine to gain a good position in [the next] six weeks which will be important for Zelensky if Trump forces a ceasefire after getting back in office."
Trump will take over as US president in January and has promised to end the Ukraine war within 24 hours of taking charge.
And insiders say Putin is open to discussing a peace deal.
Bullish Vlad is already dictating hardline terms for any deal brokered by Trump, sources say.
The Kremlin could agree to freeze conflict along frontlines - but will refuse to surrender any significant territory, five current and former Russian officials told Reuters.
Vlad's forces are continuing to gain ground and Russia claims to have grabbed more eastern territory in recent days.
Sources say there could be room for negotiation over the precise carve-up of Donetsk, Luhansk, Zaporizhzhia and Kherson.
Moscow claims the four eastern regions are wholly part of Russia - but open-source data shows up to 30 per cent is still held by Ukrainian defenders.
Analysts from the Institute for the Study of War said: "The manner in which the Kremlin is trying to set its terms for negotiations strongly signals that Russia's objectives remain unchanged and still amount to full Ukrainian capitulation.
"The Kremlin does not appear any more willing to make concessions to the incoming Trump administration than it was to the current administration."