Ukrainian presidential adviser on why Wagner rebellion is 'beginning of the end' for Russian war effort

Ukrainian presidential adviser Mykhailo Podolyak said he believes "without a doubt" that the brief armed rebellion in Russia over the weekend marks "the beginning of the end" of the war in Ukraine.

"It is the beginning of the end, but the problem is this 'end' can last for quite some time and we have to understand that," Podolyak told ABC News during an interview in Kyiv on Saturday.

"Russia has accumulated a lot of internal problems, but they are not ready to accept defeat because it would put an end to two decades of its domination in global processes," he added. "It would mean the end of Russia's ambitions, because I always said that the end of war must not mean just a victory for Ukraine. It should bring about reformatting Russia itself."

A feud between Yevgeny Prigozhin, head of the Russian paramilitary organization Wagner Group, and Russia's top military brass escalated on Friday night as Prigozhin's forces left the front line in Ukraine and marched across the border to seize the southern Russian city of Rostov-on-Don.

Prigozhin, once a close ally of Russian President Vladimir Putin, accused the Russian military of deliberately shelling his fighters in Ukraine earlier that day. Before the revolt, the mercenary leader had clashed for months with Russian Defense Minister Sergei Shoigu and Gen. Valery Gerasimov, chief of the General Staff of the Russian Armed Forces, over the conduct of the ongoing war in Ukraine.

On Saturday morning, a column of Wagner forces marched seemingly unchallenged toward Russia's capital, with Prigozhin threatening to "destroy anyone who stands in our way." But within hours, Prigozhin ordered his soldiers to halt their march on Moscow and return to their field camps in Ukraine, saying he wanted to avoid shedding Russian blood. The Kremlin announced it had made a deal that Prigozhin will move to the neighbouring country of Belarus -- a staunch Putin ally -- and receive amnesty, along with his mercenaries.

The reason why the chaotic uprising came to a sudden end was a mystery, given that Prigozhin appeared to have been in a dominant position, a senior U.S. official told ABC News on Saturday. Nevertheless, the 24-hour mutiny was the most significant challenge to Putin's authority in his more than 20 years of rule.

Podolyak, adviser to the Head of the Office of the President of Ukraine, told ABC News that he believes the political turmoil is "the first stage of a huge civil war" in Russia.

"Whether someone wants it or not, Russia will have to go through it," he said during the interview on Saturday.

Ukrainian intelligence had previously indicated that such events may happen and could bring "closer" the end of Russia's 16-month-old invasion of Ukraine, according to Podolyak.

"We definitely understand that the events we are seeing today in Russia can significantly speed up the process of bringing an end to the war and significantly speed up the beginning of the transformation of the political system in Russia itself," he added.

When asked whether his country had any role in the Russian mutiny, Podolyak told ABC News: "Ukraine is undoubtedly involved in what's going on in Russia today."

"We're defeating Russia on the battlefield, thus dismantling the myths on which Russia was based and around which Putin's power structure has been built," he said. "So it gives the opportunity to other players -- both political, military and others -- to claim their stakes, to declare their ambitions. So we are involved in all those events and the more defeats we inflict on Russia, the faster the end will come to Russia as it is now. And this is important not just for territorial integrity and sovereignty of Ukraine, but for future global security."

Podolyak noted that the Ukrainian counteroffensive, launched earlier this month, is only in its early stages and "the intensity of our operations will gradually grow."

"The intensity of strikes on Russian logistics will grow," he added, "and we will increase pressure on the first and second lines of Russian defense."