The Kremlin has accused Joe Biden’s outgoing US administration of wanting to escalate the conflict in Ukraine by allowing Kyiv to use long-range missiles for strikes inside Russia, vowing an “appropriate and palpable” response.

The decision, first reported on Sunday, to allow Ukraine to conduct strikes with US-made weapons deep into sovereign Russian territory has not been formally announced by the White House, but a German government spokesperson said on Monday that Berlin had been informed.

“It is clear that the outgoing administration in Washington intends to take steps to continue to add fuel to the fire and to further inflame tensions around this conflict,” Vladimir Putin’s spokesperson, Dmitry Peskov, told reporters. “This decision is reckless, dangerous, aimed at a qualitative change, a qualitative increase in the level of involvement of the United States.”

Russia’s foreign ministry said in a statement that the use of long-range US-supplied missiles against its territory would “represent the direct involvement of the United States and its satellites in hostilities against Russia.” It added: “Russia’s response in such a case will be appropriate and palpable.”

Biden, currently in Rio de Janeiro for his final G20 Summit, has yet to comment on the decision, which marks a significant shift in US policy.

The Ukrainian president, Volodymyr Zelenskyy, had long pushed for authorisation from Washington to use the 190-mile range Army Tactical Missile System, known by its initials Atacms, to hit targets inside Russia.

Peskov said Putin had expressed his position clearly in September when the Russian leader warned that the move to let Kyiv use longer-range weapons against targets inside Russia would mean Nato would be directly “at war” with Moscow.

Putin had said Moscow would “take the appropriate decisions based on the threats that we will face” and previously suggested Moscow could supply long-range weapons to other countries with the aim of attacking western targets.

“If someone thinks it is possible to supply such weapons to a war zone to attack our territory and create problems for us, why don’t we have the right to supply our weapons,” Putin told a press conference in St Petersburg in June.

Russian officials similarly pledged that Moscow would respond to Biden’s decision, though they did not elaborate on what that response might entail.

Leonid Slutsky, the chair of the ultranationalist Liberal Democratic party of Russia, said the US was now directly participating in the military conflict in Ukraine. “This will inevitably entail the toughest response from Russia, based on the threats that will be posed to our country,” he said.

There were further Russian threats issued in state media, with the prominent propagandist Dmitry Kiselyov saying the west was directly entering the war “with all the ensuing consequences for their own territories and those inhabiting them”. Kiselyov said: “The response could be anything. Anything.”

On Monday, the Kremlin rejected a reported peace proposal from the Turkish president, Recep Tayyip Erdoğan, to be put forward at the G20 summit in Brazil, to freeze hostilities at the current positions of both parties.

“Any option involving the freezing [of the conflict] along the line of engagement is unacceptable for Russia in any case,” Peskov said, adding that Putin had declared Russia’s demands for ending the war in June when he said Ukraine would have to drop its Nato ambitions and withdraw all its troops from all the territory of four regions claimed by Russia.

The US decision is being justified by the presence of North Korean troops fighting alongside Russia against Ukraine. Briefings to US journalists said permission to use the missiles would be limited to the Kursk region, where Ukraine launched an incursion into Russia in the summer.

Several western officials praised the US decision to permit Ukraine’s use of long-range missiles. “Ukraine should be able to use the arms we provide in order not only to stop the arrow but also to be able to hit the archers,” the EU’s chief diplomat, Josep Borrell, said before a meeting of EU foreign ministers in Brussels on Monday.

The German foreign minister, Annalena Baerbock, described Biden’s decision as “important” and “essential”. She said in Brussels: “The decision from the American side, and I would like to emphasise that this is not a rethink but an intensification of what has already been delivered by other partners, is so important at this moment.”

A German government spokesperson said, however, that Germany was sticking with its decision not to supply Kyiv with long-range Taurus missiles. The decision by the chancellor, Olaf Scholz, to withhold its most powerful missile has been a significant point of contention in Germany.

“The chancellor’s decision is unchanged,” the German government spokesperson told a regular news conference in Berlin. Last week, Scholz held a telephone conversation with Putin about the war in Ukraine, in a move that drew criticism from Kyiv.

The UK on Monday refused to say whether its ongoing support for Ukraine would include allowing UK-supplied Storm Shadow missiles to be fired at targets in Russia.

Meanwhile, France said it was still considering whether to allow Ukraine to use its long-range Scalp missiles inside Russia. Jean-Noël Barrot, the minister for Europe and foreign affairs of France, said: “We openly said this was an option that we would consider if it was to allow to strike a target from where Russia is currently aggressing Ukrainian territory. So nothing new on the other side.”

But there was also criticism in Europe from Hungary, seen as Putin’s closest EU ally.

“The pro-war mainstream has launched its last, desperate attack on the new reality”,” the Hungarian foreign minister, Péter Szijjártó, wrote on Facebook, referring to the recent victory of Donald Trump.

“The hawkish politicians ousted from power refuse to take note of the will of the people. This is not only undemocratic, but also extremely dangerous,” Szijjártó added.

Trump’s team are yet to officially comment on Biden’s move. The president-elect’s son Don Jr criticised the decision, writing on X: “The military industrial complex seems to want to make sure they get world war three going before my father has a chance to create peace and save lives. Gotta lock in those $trillions. Life be damned! Imbeciles!”

Elon Musk, a close Trump ally, claimed on his social media platform, X, that Russia would “respond reciprocally” to the US approval.

Some Russian officials openly voiced hopes that the incoming Trump administration would overturn the decision after taking office in late January.

“These guys, Biden’s administration, are trying to escalate the situation to the maximum while they still have power and are still in office,” the Russian lawmaker Maria Butina said. “I have a great hope that Trump will overcome this decision if this has been made because they are seriously risking the start of world war three, which is not in anybody’s interest.”