President Joe Biden has lifted that ban on Ukraine’s use of US-supplied long-range missiles meaning the war-torn country can now strike deep inside Russia, sources say.

The decision is a major US policy shift and comes as Biden is about to leave office and President-elect Donald Trump has pledged to limit American support for Ukraine and end the war as soon as possible.

US officials briefed the New York Times on the move in the wake of one of Russia’s biggest aerial bombardments of Ukraine in the war on Saturday night.

The weapons are likely to be used in response to North Korea’s decision to send thousands of troops to Russia in support of Russian President Vladimir Putin’s invasion of Ukraine, according to one of the sources.

Around 10,000 soldiers from the communist regime have joined the fight to reclaim Kursk, which Ukraine seized in a daring counter offensive last August.

Mr Biden hopes that this response will ‘send a message’ to Kim Jong Un not to send any more, sources said.

Ukraine plans to conduct its first long-range attacks in the coming days, according to sources. The first deep strikes are reportedly likely to be carried out using ATACMS rockets, which have a range of up to 190 miles.

Biden allowing Volodymyr Zelensky’s forces to use US-supplied missiles for strikes deep into Russia has raised expectations for the UK to follow suit with its Storm Shadow missiles.

Keir Starmer has previously said that he would be in favour of giving the green light for the Storm Shadow missiles to be used and his French counterpart Emmanuel Macron echoed this sentiment, which might mean that France could also soon allow Ukraine to fire their supplied long-range missiles into Russia.

Russia is set to launch a major assault with some 50,000 soldiers to retake Kursk.

The ATACMS missiles can strikes Russian and North Korean troop concentrations, key pieces of military equipment, logistics nodes, ammunition depots and supply lines deep inside Russia.

Mr Zelensky has repeatedly argued that being able to strike inside Russia would blunt Moscow’s advances and disrupt its ability to launch devastating missile attacks on Kyiv.

Britain tried to table a plan to allow Ukraine to use UK-supplied Storm Shadow missiles, but they are reliant on US navigation systems to be effective and Washington blocked the move.

Zelensky has been pressing Biden for months to allow Ukraine to strike military targets deeper inside Russia with US-supplied missiles, saying the ban had made it impossible for Ukraine to try to stop Russian attacks on its cities and electrical grids.

He said about Biden’s decision: ‘Today, many in the media are saying that we have received permission to take appropriate actions. But strikes are not made with words. Such things are not announced. The missiles will speak for themselves.’

While some US officials have expressed skepticism that allowing long-range strikes will change the war’s overall trajectory, the decision could help Ukraine at a moment when Russian forces are making gains and possibly put Kyiv in a better negotiating position when and if ceasefire talks happen.

Biden had remained opposed until now, determined to hold the line against any escalation that he felt could draw the US and other NATO members into direct conflict with Russia.

But North Korea has deployed thousands of troops to Russia to help Moscow try to claw back land in the Kursk border region that Ukraine seized this year, which could have contributed to Biden changing his mind.

Former senior NATO official Nicholas Williams has called the decision to allow Ukraine to fire US-supplied missiles into Russia ‘significant in terms of the end game’.

‘It is significant. The Ukrainians may say it’s too little too late but it’s not too late to affect the end game,’ he told Sky News.

Williams also said the decision was important for ‘positioning Ukraine to not make the significant concessions which Russia wants in order to get peace’.

The introduction of North Korean troops to the conflict comes as Moscow has seen a favorable shift in momentum. Trump has signaled that he could push Ukraine to agree to give up some land seized by Russia to find an end to the conflict.

As many as 12,000 North Korean troops have been sent to Russia, according to US, South Korean and Ukrainian assessments.

US and South Korean intelligence officials say North Korea also has provided Russia with significant amounts of munitions to replenish its dwindling weapons stockpiles.

It is not clear if Trump will reverse Biden’s decision when he takes office in January.

The surprise move from the White House came as Vladimir Putin’s forces looked to freeze the population of Ukraine this winter.

NATO was forced to scramble the Polish and Romanian air force as over 200 missiles and drones aimed to wipe out their eastern neighbour’s energy grid, causing blackouts across the country.

The US-made MGM-140 Army Tactical Missile System (or ATACMS), designed and manufactured by the US defence company Ling-Temco-Vought (LTV), can fly up to 190 miles (roughly the same distance from London to the outer suburbs of Paris).

To put that into Ukrainian terms, the US missiles can reach from Ukrainian-controlled territory, well into Russia’s borders, putting just about any target within Ukraine into Kyiv’s crosshairs – including all of Crimea – which one analyst said could be rendered ‘militarily worthless’ by the weapons, according to Business Insider.

ATACMS are launched by either Multiple Launch Rocket Systems (MLRS) or High Mobility Artillery Rocket Systems (HIMARS) – both military trucks that double-up as missile launchers.

There are four variants of the ATACMS, two of which – the M39 Block I and the M39A1 Block I – contain 950 and 300 M74 bomblets respectively.

Each of these bomblets is roughly the size of a baseball, and in the case of the M39, 950 are dispersed over an area of 677 feet in diameter – covering 360,000 square feet – making them highly effective at destroying groups of parked aircraft, ammunition dumps, aid defence systems – as well as gatherings of troops.

On Saturday night, Putin launched a devastating salvo of 120 cruise and ballistic missiles as well as 90 drones that killed at least 10.

Terrified Ukrainian civilians were seen cowering in bomb shelters in Kyiv as while air defences shot down dozens of missiles ‘severe damage’ was inflicted on the power grid.

The country’s energy operator DTEK announced emergency power cuts at around 7am UK time on Sunday morning affecting the Kyiv, Donetsk and Dnipropetrovsk regions following overnight drone strikes.

It said shortly thereafter thermal power plants had been struck by Putin’s latest fusillade. The level of damage was not immediately clear.

Air defences were deployed overnight to intercept drones in Kyiv as residents were urged to take cover, while missiles bound for the west of the stricken country prompted NATO to send out its warplanes to assist.

‘Due to the massive attack by the Russian Federation using cruise missiles, ballistic missiles and unmanned aerial vehicles on objects located, among others, in western Ukraine, Polish and allied [NATO] aircraft have begun operating in our airspace,’ said a statement from the Polish operational command.

‘On-duty fighter pairs were scrambled, and the ground-based air defence and radar reconnaissance systems reached the highest state of readiness. The steps taken are aimed at ensuring safety in areas bordering the threatened areas.’

The ferocious overnight attack took place 24 hours after German Chancellor Olaf Scholz extended an olive branch to Vladimir Putin for the first time since his illegal invasion.

He called the dictator on Friday in an attempt to open a dialogue on peace plans after Donald Trump was swept to power in the US promising to end the war.

Trump is also reported to have held a call with Putin where he told him not to escalate the conflict before his inauguration in January – though the Kremlin denies this.

Polish PM Donald Tusk took aim at Scholz and Trump, tweeting on Sunday: ‘No-one will stop Putin with phone calls.

‘The attack last night, one of the biggest in this war, has proved that telephone diplomacy cannot replace real support from the whole West for Ukraine.

‘The next weeks will be decisive, not only for the war itself, but also for our future.’

Sir Keir Starmer said he had ‘no plans’ to speak to Mr Putin, urging ‘full support as long as it takes’ as he headed to a meeting of G20 leaders in Rio.

The Prime Minister Sir Keir told reporters: ‘It’s a matter for Chancellor Scholz who he speaks to. I have no plans to speak to Putin. We are coming up to the 1,000th day of this conflict on Tuesday.

‘That’s 1,000 days of Russian aggression, 1,000 days of huge impact and sacrifice in relation to the Ukrainian people and recently we’ve seen the addition of North Korean troops working with Russians which does have serious implications.

‘I think on one hand it shows the desperation of Russia, bit it’s got serious implications for European security […] and for Indo-Pacific security and that’s why I think we need to double down on shoring up our support for Ukraine and that’s top of my agenda for the G20.

‘There’s got to be full support as long as it takes and that certainly is top of my agenda, shoring up that further support for Ukraine.’