The chief of the Baltic state’s foreign intelligence service, issued the warning on Tuesday.
Speaking as he a released a national security threats report, Kaupo Rosin said Russia “has chosen a path which is a long-term confrontation”.
“The Kremlin is probably anticipating a possible conflict with Nato within the next decade or so,” He said, according to Reuters.
He added attack on the West by Russia is “highly unlikely” in the short term and would be less likely if Nato built up its conventional military forces in Europe.
“If we are not prepared, the likelihood [of a military Russian attack] would be much higher than without any preparation,” Rosin said.
Estonia is one of the European Nato allies which has a border with Russia to its east and would be on the frontline of any conflict should it spread beyond Ukraine.
On Tuesday Russia placed Estonian prime minister Kaja Kallas on a wanted list.
Estonia’s warning comes after Donald Trump said he would “encourage” Russia to “do whatever the hell they want” to other Nato members.
His intervention drew a backlash from many Western allies of the US, including foreign secretary David Cameron who said it was “not a sensible approach”.
As of last year, Trump would not have the power as president to unilaterally withdraw the US from Nato and would have to seek. approval from the US congress.