Russian President Vladimir Putin became enraged and conspicuously blundered during the 2015 Minsk Agreement talks with Ukraine, according to a book by former French President Francois Hollande.

Russia illegally annexed Crimea from Ukraine in 2014.

The US, the European Union, and other observers say Russia has slyly used troops posing as Ukrainian separatists to stoke a war there for years.

But when Putin was arguing with Ukraine's president, Hollande said, he appeared to slip up and acknowledge the presence of Russian troops in Ukraine.

He made other embarrassing blunders at the meeting too, Hollande wrote.

Russian President Vladimir Putin became so enraged during a shouting match with Ukrainian President Petro Poroshenko that he revealed he was lying about Russia's role in a military uprising in eastern Ukraine, former French President Francois Hollande wrote in a book published earlier this year about his time in office.

In 2014, Russia illegally annexed Crimea from Ukraine and began to support separatists in the eastern part of the country through information warfare, direct shipments of weapons, and the deployment of Russian fighters posing as Ukrainian separatists.

Experts branded the campaign, for which Russia denied responsibility, as a new form of conflict called hybrid warfare. The strategy involves multidomain fighting, economic pressure, and a distortion of facts on the ground.

But in a heated argument with Poroshenko at the 2015 talks to form the Minsk Agreement, a document that sought to end the conflict but that Russia has yet to implement, Putin apparently became so angry he tripped up.

"Poroshenko and Putin constantly raised their voices with each other. The Russian president was so worked up, that he started threatening to decisively crush his counterpart's forces," an excerpt from Hollande's 2018 book, "The Lessons of Power," says, according to a translation by UAWire.org, which writes about Russia and Ukraine.

"This showed that there are Russian troops in eastern Ukraine. Putin suddenly realized, and got a grip on himself,” Hollande wrote, according to UAWire.org.

But even after Putin got ahold of himself, his narrative continued to unravel, Hollande wrote.

In Minsk, Poroshenko asserted Ukraine's sovereignty as its leader. Putin would not acknowledge directing any of the separatist forces and constantly had to frame his contributions to the conversation as speculation on what the separatists might say, if they were there.

Hollande wrote that Putin tried to delay the cease-fire between the fighting sides for weeks. When Hollande and Poroshenko brought up that Russia had been sanctioned as result of the fighting, and not a nebulous group of unnamed fighters, Putin "pretended not to understand or not to hear what we were saying," Hollande wrote.

“At seven in the morning after a sleepless night," both sides finally struck a deal that Putin could agree to, Hollande wrote. But Putin, maintaining he wasn't in control of the separatists, had to run off, Hollande wrote.

"Suddenly Putin said that he needed to consult with the separatist leaders. Their emissaries were in Minsk too. Where exactly? In some hotel or in an office neighboring ours? At least we didn’t see them," Hollande wrote.

Fighting continues in eastern Ukraine, with more than 10,000 dead. Russia still denies any official involvement in the fighting and remains under the sanctions imposed in 2014.