Andrei Illarionov, an outspoken Kremlin critic who served as chief economic adviser to Putin from 2000 to 2005.
A former adviser to President Vladimir Putin, Andrei Illarionov, has said Moscow might be planning to take over other territories that used to be part of the Russian empire, including Belarus, the Baltic states and Finland.
In an interview with Swedish newspaper Svenska Dagbladet, Illarionov said Putin would be looking to correct past "big mistakes" in other former Russian territories.
Illarionov, an outspoken Kremlin critic who served as chief economic adviser to Putin from 2000 to 2005, said Putin could argue that the Bolsheviks' decision to grant independence to Finland in 1917 was "treason against national interests."
"Putin's view is that he protects what belongs to him and his predecessors. Parts of Georgia, Ukraine, Belarus, the Baltic states and Finland are states where Putin claims to have ownership," said Illarionov, who now works as a senior fellow at the Cato Institute in Washington.
His comments echoed Western fears that Putin might not stop with the annexation of Crimea from Ukraine and use force to reclaim other land as part of a policy of Russian expansionism.
"It is not on Putin's agenda today or tomorrow," Illarionov said. "But if Putin is not stopped, the issue will be brought sooner or later."
Illarionov quit his position as Putin's aide in December 2005 after six years in the post and amid repeated disagreements with the Kremlin over what he has called "its lack of liberal or even mainstream policies."