BERLIN — Nobel laureate Günter Grass’s surprise disclosure that he served in the Waffen-SS as a teenager met with sympathy from some fellow German writers but also drew harsh criticism from literary and political figures, including Poland’s former president and Nobel Peace Prize winner, Lech Walesa, who asked why he waited so long.

The author of the classic “The Tin Drum” and many other writings, Mr. Grass, has for decades stood as his country’s literary conscience, urging Germany to face up to its Nazi past and warning against any resurgence of imperial ambition. Critics say the 78-year-old’s moral authority has been undermined by his silence about his months in the military arm of Adolf Hitler’s notorious SS.

It was previously known that Mr. Grass did military service and was wounded, ending up as a prisoner of American forces, but he never mentioned the Waffen-SS.

Mr. Walesa said Mr. Grass should voluntarily give up his honorary citizenship in Gdansk, Poland, called Danzig at the time. Mr. Grass was born there in 1927.

“I have had the luck, as a Nobel winner from Gdansk, that we have never met. That has saved me from having to shake his hand,” Mr. Walesa said in an interview in the Dziennik daily published yesterday. “Today, I would not shake his hand.”

A biographer of Hitler and one of the country’s most prominent chroniclers of the Nazi period, Joachim Fest said Mr. Grass’s silence was “totally inexplicable.”

“I do not understand how someone can elevate himself constantly for 60 years to the nation’s bad conscience, precisely in Nazi questions, and only then admit that he himself was deeply involved. I don’t know how he could play this double role for so long,” Mr. Fest was quoted as saying by the Bild newspaper in yesterday’s edition.

“He is seriously damaged. To use a common saying: I wouldn’t buy a used car from this person.”

But some writers expressed their support, stressing Mr. Grass’s short service in the military and his disclosure that he was swayed by the Nazis’ sophisticated efforts to indoctrinate young people.

Mr. Grass said he applied at 15 for the submarine service and was turned down; he was accepted by the military at 17, but when he reported for duty in Dresden in early 1945, he discovered it was with the 10th SS Panzer Division “Frundsberg.”

“Anyone who looks more closely will likely feel sympathy with an adolescent misled by Nazi propaganda, whose ambition drove him into the Waffen-SS,” a commentator, Stefan Reinecke, wrote in the left-leaning Taz daily.

Some observers questioned the timing of the disclosure for other reasons: They said the controversy will not hurt sales of his forthcoming book, “Peeling the Onion.”The 480-page memoir is set for release on September 1 by the Goettingen-based Gerhard Steidl publishing house.

“Günter Grass thought for a long time how he could get the most possible people to buy his new memoir,” a columnist, Hans Zippert, wrote in Die Welt. “Then, fortunately, it occurred to him that he had been a member of the Waffen-SS but hadn’t trumpeted it before.A real sensation!”

Milder criticism came from Vice Chancellor Franz Müntefering, a leading member of the Social Democrats, whom Mr. Grass has long supported.”It would have been good if it were earlier,” he said on n-tv television.

Mr. Müntefering said he still respected Mr. Grass and was glad he had not had to face a similar situation in his own youth.

Mr. Grass has acknowledged that, at the time, he looked on the Waffen-SS as an elite unit, not as something repulsive. He added in his interview with the Frankfurter Allgemeine Zeitung, published Saturday, that he dodged training for several weeks by giving himself jaundice, but he gave few details. The newspaper reported that Mr. Grass said he did not fire a shot between call-up in February 1945 and being wounded that April 20, near the end of the war.

He said he had felt shame about his SS service and was disclosing it now because “it weighed on me.”

Mr. Grass’s division fought Soviet forces in eastern Germany near the war’s end. Some of its members fled west to surrender to American troops on the Elbe River.

The SS, headed by a top Nazi, Heinrich Himmler, began as a small personal bodyguard unit for Hitler but later grew into a sprawling organization that carried out mass executions of Jews and opponents of the Nazis. One part of the SS ran concentration camps.

The combat wing, the Waffen-SS, campaigned alongside regular army troops and gained a reputation as fanatical fighters. Waffen-SS units helped wipe out resistance by Polish Jews in the Warsaw Ghetto and slaughtered American prisoners of war near the Belgian town of Malmedy during the Battle of the Bulge in 1944.

The SS was declared a criminal organization by the Nuremberg war crimes tribunal after the war.