Senior Russian politicians have declared President Joe Biden has taken a 'big step towards World War Three' after his administration reportedly gave the green light for Ukraine to blast targets inside Russia with US-supplied long-range missiles.  

The decision, which came on the eve of the 1000th day of war in Ukraine amid the dying days of the Biden administration, heralded a torrent of apocalyptic warnings from Russian lawmakers. 

'This is a very big step towards the beginning of the Third World War,' said Putin-loyalist Vladimir Dzhabarov, deputy chairman of the foreign affairs committee of the upper house and a retired security service general.

He slammed the move from Biden - 'a departing old man who will no longer be responsible for anything in two months'.

Hardline Liberal-Democatic party leader Leonid Slutsky said: 'Biden has apparently decided to end his presidential term and go down in history as Bloody Joe.

'It will mean only one thing - direct US participation in the military conflict in Ukraine, which will inevitably entail the harshest response from Russia, based on the threats that will be created for our country.'

Russian senator Andrey Klishas said: 'The West has decided on a level of escalation that could end with the remnants of Ukraine completely losing their statehood.'

Putin himself is yet to respond to the major change in Western policy.

But in October, he warned that long-range missile strikes on his territory would mean the West was 'at war with Russia' because only NATO specialists - and not Ukrainians - could fix these missiles onto their targets. 

'If this is the case, then, bearing in mind the change in the very essence of this conflict, we will make appropriate decisions based on the threats that will be posed to us,' Putin said.

One Russian official urged Britain and France to refuse to follow the Biden administration's tack by allowing Ukraine to deploy Storm Shadow and SCALP long-range missiles in Russia. 

Unconfirmed reports from Le Figaro indicated both London and Paris were considering their position after months of having refused Zelensky's pleas to use the fearsome munitions on Russian targets.

Senior Russian diplomat Mikhail Ulyanov, the Kremlin's permanent representative to international organisations in Vienna, said: 'They have a chance to reconsider their position if they are truly concerned about European security.

'There is no longer room for primitive political games.'

Downing Street is yet to issue a response to Biden's decision, which has not been officially announced but has been widely reported in the US.

But Sir Keir Starmer said 'we need to double down' on support for Ukraine and the issue was 'top' of his agenda at this week's G20 summit of world leaders in Brazil.

Biden will be at the gathering, while Russia will be represented by foreign minister Sergei Lavrov.

In the US, Biden's move riled supporters of President-elect Donald Trump, who pledged to limit American support for Ukraine and end the war as soon as possible.

Trump's oldest son, Donald Trump Jr, posted on X after Biden's decision was announced, saying that 'the military industrial complex seems to want to make sure they get World War 3 going before my father has a chance to create peace and save lives'.

David Sacks, a tech millionaire who was a major donor for Trump's presidential campaigner, added that Biden permitting Ukraine to use US-supplied missiles in Russia would 'massively escalate' the situation. 

'President Trump won a clear mandate to end the war in Ukraine. So what does Biden do in his final two months in office? Massively escalate it. Is his goal to hand Trump the worst situation possible?' Sacks said. 

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

Ukrainian President Volodymyr Zelensky noted that the reports about Biden's policy change - which reportedly would authorise the use of Western missiles to strike targets in the Kursk region only - had not been openly confirmed by the White House but said the 'missiles will speak for themselves'.

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

Former senior NATO official Nicholas Williams 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 weapons are likely to be used in response to North Korea's decision to send thousands of troops to Russia in support of Putin's invasion of Ukraine, according to sources.  

Around 10,000 soldiers from the pariah state have joined the fight to reclaim Kursk, parts of which Ukraine seized in a daring counter offensive in August. 

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

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.

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.

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. 

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. 

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

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.

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,' the Polish operational command said in a statement.

'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 came 24 hours after German Chancellor Olaf Scholz extended an olive branch to 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 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 - 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.'

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

The Prime Minister 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.'