The two presidents, who forged a strong friendship in over a decade in power, have traded a slew of insults since Turkey shot down a Russian warplane on November 24 on the Syrian border for alleged repeated violations of its airspace.
Putin has accused the Turkish leadership of importing oil from IS extremists in Syria, an accusation that Erdogan rubbished as a "slander" so untrue that the Russian leader should consider his position.
The pair have based their still considerable domestic popularity on projecting an image of political virility in their post-imperial societies and are unlikely to show any sign of being the first to back down, analysts say.
They could be at each other's throats until 2024 -- the next presidential elections in Russia are due in 2018 and Turkey in 2019 where Putin can pick up a new six-year mandate and Erdogan a five-year extension.
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"They tend to get deeply dug in and not to back down. And I don't think either is prepared to do so anytime soon," said Philip Gordon, senior fellow at the US-based Council on Foreign Relations (CFR).
The venomous rhetoric of Putin, who Thursday described the Turkish leadership as a "ruling clique" deprived of common sense, and the Turkish leader's defiant refusal to apologise will make it hard to paddle back.
Fredrik Wesslau, senior policy fellow at the European Council on Foreign Relations (ECFR), said that the dispute had turned so personal because the legitimacy of both men depended on "coming out on top".
"Their credibility would be undermined by a demonstration of weakness, by, for instance, apologising or making a conciliatory gesture."
Their personal relations had been marked by a firm desire not to let differences on issues like the Syria or Ukraine crises -- let alone the centuries of war waged by the Ottoman and Russian Empires -- impede strategic cooperation.
There also seemed a genuine personal bond between two men who had both led their nations out of economic crisis to a new era of stability but been criticised as ruling with the same authoritarianism as a Russian tsar or Ottoman sultan.
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Just nine days ahead of the shooting-down of the plane, Erdogan had welcomed Putin to a G20 summit in the Turkish resort of Antalya like an old friend.
Under their leadership, visas were scrapped for citizens of both countries, an ambitious project for a Black Sea gas pipeline was agreed and Russia began work on Turkey's first nuclear power plant.
On a visit to Russia in November 2013, Erdogan even suggested Turkey could join the Moscow and Beijing-led security group the Shanghai Cooperation Organisation (SCO) and join Putin's Eurasian Economic Union, moves that could have scuppered Turkey's long-standing EU membership bid.
But in the last 10 days alone, Russia has said it will re-impose visas for Turks, suspended talks on the TurkStream pipeline and refused to guarantee that work on the Akkuyu nuclear power plant will continue. Meanwhile, Turkey's long-stalled EU bid has regained momentum.
"I am very sorry as I personally invested a lot into building these relations," Putin said.
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Erdogan expressed nostalgia for the good old days where he and Putin, as well as the Russian leader's favourite foreign chums ex-Italian premier Silvio Berlusconi and former German chancellor Gerhard Schroeder, would get together.
"He (Putin) always talked about my bravery and boldness. He also commented a lot about my honest statesmanship," Erdogan lamented.
The breakdown of the relationship also has implications well beyond Russia and Turkey, with narrowing the differences between the two countries on Syria seen as crucial to ending the conflict there and defeating Islamic State (IS) extremists.
Just before the plane incident, US President Barack Obama had hailed talks between global and regional powers in Vienna as the first halting progress towards finding a solution.
"These countries are in the deep freeze, which will make the US job of brokering something in Vienna all the more difficult," said Gordon.
Putin's trusted Kremlin chief of staff Sergei Ivanov said Thursday the two leaders' relationship will "definitely" never be the same again.
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