VLADIMIR Putin is preparing for a new invasion of Ukraine using 500,000 troops, Ukraine's defence minister has said.
Oleksii Reznikov said Russia could "try something" to mark the anniversary of the initial invasion last year.
The fresh assault would also mark Russia's Defender of the Fatherland Day on 23 February, which celebrates the army.
Mr Reznikov said: "Officially they announced 300,000 but when we see the troops at the borders, according to our assessments it is much more."
It comes after the Institute for the Study of War (ISW) claimed an "imminent" offensive on the war-torn nation is "the most likely course of action".
Kyrylo Budanov, the head of Main Military Intelligence Directorate (GUR), said he expects the fresh wave of attacks to be focused on the Luhansk Oblast in the east of the country.
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Budanov also stated that Ukraine is preparing for its own counteroffensive "from Crimea to Donbas" and intends to retake occupied Crimea by the middle of this year.
Despite some heavy fighting in the eastern Donbas region, the war has entered a stalemate in recent months following the reclaiming of the southern city of Kherson from Russia.
Kremlin forces have reportedly been expelling Ukrainian civilians from their homes in eastern regions as they gather their military might.
GUR representative Andrii Yusov told Ukrainian TV that the country was on the eve of a "very active phase of the war".
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He added: "Both February and March will be intensive.
"The skill and motivation of Ukrainian soldiers, plus their equipment and weapons, both domestic and [those sent as] help from international partners, are what will ultimately turn the tide of these offensive actions."
Likewise, Oleksiy Danilov, chair of Ukraine’s national security and defence council, said Russia is preparing for a "maximum escalation, gathering all possible forces" for a new assault.
A Russian spring offensive has long been considered likely.
Meanwhile, a senior Ukrainian soldier has urged Russian forces to abandon their posts before they are killed in Mad Vlad's war of aggression.
Lieutenant General Yurii Sodol, head of Ukraine's marines, said: "I will separately address the Russian military: before it's too late, run, return to your "Maruskas" [Russian women] or surrender, otherwise it's the fate of a fertiliser on someone else's land; a black bag or disability awaits you, this is your "happy" future.
"Unlike you, we know what we are fighting for, we are united, we are one.
"We will do everything so that the blue-yellow flag flies again in all cities of Donbas and Crimea."
Lieutenant General Sodol also predicted that thousands of Russian troops were set to invade in the coming months.
Moscow's response was to accuse NATO of mobilising all its military infrastructure against Russia, even including satellites.
Kremlin spokesman Dmitry Peskov said the move created "very peculiar, hostile conditions" for Russia and that his government has taken notice.
However, the country's troops seem to be floundering on the battlefield, as a leaked phone call between front-line forces revealed.
One soldier called the campaign a "meat grinder" and that basic supplies like water were heavily rationed.
It comes after Jens Stoltenberg, the NATO secretary-general, warned that Russia was mobilising 200,000 troops for a fresh offensive.
Ukraine have detailed the 'war chest' of new weaponry that they want the West to provide to repel the attack, but the US stopped short of sending F-16 fighter jets.
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British Defence Secretary Ben Wallace has told reporters that it would "not be the right approach" to send jets but said no "solid decision" had been made.
Likewise, Moscow mouthpiece Peskov warned that long-range rockets which are believed to be included in an upcoming support package for Ukraine from the US would "escalate" the conflict.