"I do not want to be a prophet of doom, but there is a risk that the Russian aggression in Ukraine will not end. A analysis of the sequence of actions in Putin’s policy indicates this," he said.

According to Brzezinski, further developments depend on how the conflict develops in Ukraine.

"If the war in Ukraine becomes a light military success for Russia, or a victory, it is necessary to take into account the possibility of something like it in the Baltic States," he said.

"The next hot spots may appear in Moldova, Georgia and Azerbaijan. This could be the logic of events. And later, Poland could be the target of Russian aggression," Brzezinski said.

"Russia is now carrying out an expansive policy, and each [of these] scenarios is, unfortunately, realistic."