Angela Merkel warned that isolating Russia isn’t possible long term even if Russian President Vladimir Putin made a "big mistake” by invading Ukraine, in the former German chancellor’s tentative return to the public arena.

"There’s no excuse for this brutal aggression,” the 67-year-old said on Tuesday in an on-stage interview at a theater in central Berlin. While she has remained active behind the scenes, it was her first public appearance in front of a larger audience since leaving office in December.

She broke her silence on the war in Ukraine last week for the first time since Putin ordered the attack three months ago. At a private event organized by a labor union group, she condemned Russia’s "barbaric war of aggression” and spoke about a "profound break” in Europe’s post-war history.