BERLIN — Günter Grass, Germany’s most famous living writer, tried Friday to quell the growing controversy over a poem critical of Israel that he published this week, saying that he did not mean to attack the country wholesale but only the policies of the current government.

However, three days of worldwide debate, including a stinging personal rebuke from Israel’s prime minister, Benjamin Netanyahu, show no sign of subsiding.

The nine-stanza, 69-line poem, “What Must Be Said,” appeared Wednesday on the front of the culture section of the Munich-based newspaper Süddeutsche Zeitung. Mixing lyrical turns of phrase with discussions of the need for international supervision of both Israel’s and Iran’s nuclear programs, it bluntly called Israel a threat to world peace for its warnings that it might attack Iran’s nuclear facilities. By supplying weapons to Israel, including submarines, Germany risked being complicit in “a foreseeable crime,” Mr. Grass wrote.

“Why do I say only now, aged and with my last drop of ink, that the nuclear power Israel endangers an already fragile world peace?” his poem asks. “Because that must be said which may already be too late to say tomorrow.”