Vladimir Putin once threatened that he could have Russian troops in six capital cities in just two days, it is claimed.
The Russian president is said to have warned former Ukrainian President Petro Poroshenko that he could have soldiers on the ground in Ukraine, Poland, Latvia, Lithuania, Estonia and Romania within 48 hours.
His forces are currently bogged down with fierce fighting after failing to secure the swift invasion of Ukraine he expected.
In his remarks, reportedly made in 2014, Putin claimed that he could have soldiers in the capitals of all six countries within two days.
German newspaper Suddeutsche Zeitung reported that the Russian president told Mr Poroshenko, who was succeeded by Volodymyr Zelensky in 2019: "If I wanted, in two days I could have Russian troops not only in Kyiv but also in Riga, Vilnius, Tallinn, Warsaw and Bucharest."
He also told Mr Poroshenko, it is claimed, "not to rely too much on the EU".
The alleged threat came after Putin reportedly said he could take the Ukrainian capital “in two weeks” as thousands of Russian troops gathered at the border.
Mr Poroshenko told the US Congress in 2014: "If they are not stopped now, they will cross European borders and spread throughout the globe."
The Kremlin later denied Putin had made the comments after they were widely reported.
Last month the Russian government falsely claimed that Russian invaders would be greeted by citizens in Ukraine, but instead have been met with strong resistance and have been unable to secure Kyiv.
It has long been feared that the Russian president plans to expand his territory into EU and NATO countries.
Earlier this month European Commission Vice President Valdis Dombrovskis warned that Putin could aim his aggression at Lithuania, Latvia and Estonia if Ukraine falls.
He said: “If we do not support Ukraine, it’s not going to stop in Ukraine."
