Former German chancellor Angela Merkel in Athens

In a public discussion marking the release of her memoir, Ms. Merkel told a packed audience at the Stavros Niarchos Foundation Cultural Center that while she was forced to play the "bad cop" in demanding tough austerity measures, she never wanted to see Greece leave the single currency.

"I was clear—I did not want Grexit," she said at the event on Wednesday, recalling clashes with her then-finance minister, Wolfgang Schäuble, who was known to be more open to the idea.

"I said no, we are a union, we have responsibilities, we can't go backwards. If Greece were to leave the eurozone, it should be the Greek people's decision, not ours."

Her remarks, made in a conversation with journalist Alexis Papachelas, come a decade after the tumultuous summer of 2015, when Greece's standoff with its international creditors led to capital controls, bank closures, and a referendum that brought the country to the brink of financial collapse.

Ms. Merkel, who was often the face of German-led austerity in Greece, acknowledged her unpopularity at the time but insisted the reforms were necessary.

"Many things changed—municipalities, the land registry," she said. "These may not have been pleasant, but the state needed tax revenue. That's just how things are."

She offered praise for the endurance of the Greek people through the difficult years. "I wondered if Germans could have coped," she said. “You are a strong and admirable people.”

Without offering an apology for her government's hardline stance, Ms. Merkel said she was pleased to see Greece's economic recovery and reaffirmed her belief in the country's central role in the European Union. "I cannot imagine the EU without Greece," she said.