XI Jinping told Vladimir Putin "change is coming" in a chilling threat to the West as he left Moscow after a landmark visit.
The ominous farewell came just hours after the Russian tyrant vowed to respond to Britain's plans to send ammunition to Ukraine - as Moscow warned the risk of a "nuclear collision" was increasing.
In the unsettling parting message on Tuesday night, Xi told Putin: "Change is coming that hasn't happened in 100 years.
"And we are driving this change together."
As he gripped Putin's hand before being waved off by the Russian despot, Xi added: "Please, take care, dear friend."
The Chinese leader travelled to Moscow on Monday to meet Putin and discuss the "no-limits friendship" between their countries.
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During his two-day visit, Xi barely mentioned Putin's shambolic Ukraine war - but insisted China had an "impartial position".
Xi said he signed an agreement with Putin - bringing their ties into a "new era" of cooperation and "deepening" their partnership.
Responding to the meeting of the two leaders, the White House urged Beijing to pressure Russia to withdraw from Ukraine to end Europe's biggest conflict since World War Two.
As Xi prepared to leave Moscow on Wednesday, air raid sirens blared across Kyiv and in Ukraine's north and east, with reports of drone strikes.
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Xi was the first leader to meet Putin since the International Criminal Court issued an arrest warrant for the president over his alleged involvement in the abductions of children from Ukraine.
Their first meeting was followed by a luxurious meal ahead of peace talks about Ukraine.
Beijing has proposed a 12-point peace plan to end the Ukraine war that would see ceasefire on both sides - but would mean a territorial loss for Ukraine.
Putin praised Xi for a peace plan he proposed last month, and blamed Kyiv and the West for rejecting it.
But the West sees the peace plan as a ploy to buy the Russian dictator time to regroup his troops and cement his grip on occupied land.
And in remarks after his summit with Xi, Putin slammed the UK's plans to send tank ammunition that contains depleted uranium to Ukraine - and warned of retaliation.
"If all this happens, Russian will have to respond accordingly, given that the West collectively is already beginning to use weapons with a nuclear component," Putin said.
Putin's warning was followed by Russian defence minister Sergei Shoigu who said the British decision left fewer and fewer steps before a potential "nuclear collision" between Russia and the West.
He told reporters: "Another step has been taken, and there are fewer and fewer left."
Depleted uranium is used in weapons as it helps them easily penetrate tanks and armour.
It is a by-product of the nuclear enriching process used to make nuclear fuel or nuclear weapons - and around 60 per cent as radioactive as natural uranium.
The mildly radioactive material is denser than lead and can breach almost any type of protection on armoured vehicles but is not a type of nuclear weapon.
It is a by-product of the nuclear enriching process used to make nuclear fuel or nuclear weapons. It is around 60 per cent as radioactive as natural uranium.
But it is highly toxic and can affect people's lungs and vital organs.
Earlier, Russian Foreign Ministry spokeswoman Maria Zakharova called the plan the "Yugoslavia scenario" - saying the ammunition caused cancer and infected the environment.
PM Rishi Sunak previously confirmed a group of four Challenger 2 tanks would be sent to Ukraine.
A Ministry of Defence spokesperson said: "Alongside our granting of a squadron of Challenger 2 main battle tanks to Ukraine we will be providing ammunition, including armour piercing rounds which contain depleted uranium.
"Such rounds are highly effective in defeating modern tanks and armoured vehicles.
"The British Army has used depleted uranium in its armour-piercing shells for decades.
"It is a standard component and has nothing to do with nuclear weapons or capabilities. Russia knows this, but is deliberately trying to misinform.
"Independent research by scientists from groups such as the Royal Society has assessed that any impact to personal health and the environment from the use of depleted uranium munitions is likely to be low."
Meanwhile, Zelensky said Kyiv has invited China to talks and is waiting for an answer from Beijing.
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"We offered China to become a partner in the implementation of the peace formula," he said.
"We passed over our formula across all channels. We invite you to dialogue. We are waiting for your answer."