Speaking to weekly newspaper Die Zeit, Gauck said Chancellor Angela Merkel's stated position that Israel's right to exist was a raison d' état or national interest for Germany could be asking too much from the next generation.
"This sentence by Mrs Merkel comes from the hearts of my generation," he said.
"Everything that we want to do should be guided by the goal that Israel should be protected as the homeland of the Jews," he said.
"This sentence hasn't just been born out of political rationale but from a deep contrition. It's a moral imperative to ourselves which makes me really worried about whether we can translate the magnitude of this demand into political action."
Gauck, who visited Israel this week, said he was not at all talking about drawing a line under the Holocaust debate. "But there's one tendency I don't want to follow – pulling the perception of the Holocaust into a quasi-religious dimension, into something surreal," he said.
Gauck's comments came as he visited Palestinian President Mahmud Abbas in Ramallah. Gauck promised Abbas that Germany would continue to provide financial aid to the Palestinians – currently amounting to €70 million a year – as long as there was no solution to the Mideast conflict.
The president urged the Palestinians not to break off peace talks with Israel, saying he had urged Israeli leaders to exercise restraint on the settlement issue. Gauck also visited the opening of a German-funded girls' school in Burin in the West Bank, saying it raised "great hopes" for building a democratic and stable Palestinian state.
Gauck also told Die Zeit that he agreed with the intention of a statement by his predecessor Christian Wulff that Islam belongs to Germany. The comment stirred huge controversy in Germany. But Gauck said he would have put it differently. "I would have simply said that the Muslims who live here belong to Germany," he said.