Russia has given support to plans by separatists which it backs in Ukraine to hold referendums, paving the way for the annexation of swathes of additional territory, a direct challenge to the West that could sharply escalate the conflict.
After nearly seven months of war, including a critical battlefield defeat in northeastern Ukraine, Putin is pondering his next steps in a conflict that has triggered the biggest confrontation with the West since the 1962 Cuban Missile Crisis.
In what appeared to be choreographed requests, Russian-backed officials across 15 per cent of Ukrainian territory - an area about the size of Hungary or Portugal - lined up to request referendums on joining Russia.
The self-styled Donetsk (DPR) and the Luhansk People's Republics (LPR), which Putin recognised as independent just before the invasion, and the Kherson and Zaporizhzhia regions have on Tuesday asked for votes.
Luhansk and Donetsk officials said the referendums would take place on September 23-27.
Asked about the referendums, Russian Foreign Minister Sergei Lavrov said: "From the very start of the operation ... we said that the peoples of the respective territories should decide their fate, and the whole current situation confirms that they want to be masters of their fate."
If Moscow formally annexed a vast additional chunk of Ukraine, Putin would essentially be daring the United States and its European allies to risk a direct military confrontation with Russia, the world's biggest nuclear power.
Dmitry Medvedev, who served as Russian president from 2008 to 2012 and is now deputy chairman of the Russian Security Council, backed the referendums, which he said would change the path of Russian history and allow the Kremlin more options for defence of what he said would become Russian territory.
"Encroachment onto Russian territory is a crime which allows you to use all the forces of self-defence," Medvedev said in a post on Telegram. "This is why these referendums are so feared in Kyiv and the West."
"It is equally important that after the amendments to the constitution of our state, no future leader of Russia, no official will be able to reverse these decisions."
Ukraine said the threat of referendums was "naive blackmail" and a sign Russia was running scared.
"This is what the fear of defeat looks like. The enemy is afraid, and obfuscates primitively," said Andriy Yermak, chief of staff to Ukrainian President Volodymyr Zelenskiy.
"Ukraine will solve the Russian issue. The threat can only be eliminated by force."
Ukraine says it will not rest until every Russian soldier is ejected from its territory. Kyiv says it will never accept Russian control over its territory and has called on the West to supply more and better arms to fight Russian forces.
US President Joe Biden warned in March that a direct confrontation between the NATO military alliance and Russia would mean World War III. Biden and NATO leaders have been careful to say that they do not want NATO troops in direct conflict with Russian troops.
The conflict in eastern Ukraine began in 2014 after a pro-Russian president was toppled in Ukraine's Maidan Revolution and Russia annexed Crimea, while Russian-backed separatists in the Donbas - which is comprised of Donetsk and Luhansk - sought to break away from Kyiv's control.