For decades, military censors have struggled to defend Israel's worst-kept secret -- that the country possesses atomic weapons.
Even as its nuclear history has leaked into declassified documents, articles and books, an official policy of "ambiguity" has endured: By refusing to confirm or deny that it has the bomb, and refraining from testing one, Israel has lived up to a quiet understanding with the United States to avoid fueling a Middle East arms race.
So why does it appear that Prime Minister Ehud Olmert finally spilled the beans?
In an interview on German television late Monday, the Israeli leader seemed to list Israel among the world's nuclear club, raising an outcry across the political spectrum here and questions about whether the long-standing policy had been abandoned.
Asked by the interviewer about Iran's calls for the destruction of Israel, Olmert replied that Israel had never threatened to annihilate anyone.
"Iran openly, explicitly and publicly threatens to wipe Israel off the map," Olmert said. "Can you say that this is the same level, when you are aspiring to have nuclear weapons, as America, France, Israel, Russia?"
Israel's newspapers reported the remark Tuesday under front-page headlines, one calling it a "nuclear slip of the lip."
Olmert's office said the quote was taken out of context and that he had been listing "responsible nations," not nuclear states. Aides also noted that the prime minister had refused several times during the interview to confirm that Israel has nuclear weapons and that he had spoken in English, not his native language.
Nevertheless, his critics pounced on the centrist prime minister for undermining a hallowed tenet of Israel's defense policy.
Yuval Steinitz, a member of parliament with the right-wing Likud Party, called for Olmert's resignation.
Silvan Shalom, a former foreign minister with Likud, said Olmert's comment could "cause great damage" to Israel's most important foreign policy goal -- mobilizing international pressure to prevent Iran from obtaining nuclear weapons.
"We are constantly being asked by our enemies why we allegedly can, and Iran cannot," Shalom said.
On the left, parliament member Yossi Beilin of the Meretz Party said Olmert's "carelessness ... might be an indication that he isn't fit to serve as prime minister."
Olmert inherited a long tradition of secrecy. Surrounded at birth by hostile neighbors, Israel began building a nuclear bomb in the mid-1950s, aided by a secret agreement with France to help construct and supply a plutonium nuclear reactor in the Negev desert.
Since 1969, the United States has accepted Israel's status as a nuclear power and not pressed it to sign the Nuclear Nonproliferation Treaty, which subjects its adherents to inspections and sanctions aimed at stopping the spread of weapons.
The consensus in the U.S. intelligence community and among outside experts is that Israel has 100 to 200 sophisticated nuclear weapons, making it the region's sole nuclear power.
Those weapons now loom as an element of tension in the Middle East.
Iran is moving to develop a large uranium enrichment plant, arousing suspicions in Israel and Western countries that its ultimate product will be atomic weapons. Iran, which says it seeks nuclear technology only for power generation, views Israel as a menace. But its suspected motives for wanting a nuclear arsenal also include a desire to gain leverage in its dealings with the West.
Some analysts believe that Israel, faced with the prospect of a nuclear-armed Iran, has been seeking a way to go public with its own capabilities to maintain a deterrent advantage. Such thinking gained credence here last week when Robert M. Gates, the incoming U.S. secretary of Defense, identified Israel as a nuclear power in testimony to a Senate committee.
"It could be that Olmert wanted to hint at Israel's capability as part of the aggressive statements he has recently been making, with the goal of warning the West that if they don't take care of Iran, Israel will," Israeli security analyst Ronen Bergman wrote in the newspaper Yediot Aharonot.
"On the other hand," he said, "this may have been a slip of the tongue."
Whatever the case, Olmert returned to a more ambiguous line Tuesday at a news conference during a visit to Berlin.
"Israel has said many times ... that we will not be the first country that introduces nuclear weapons to the Middle East," he said, repeating a formula meaning that it will not launch a first strike from its arsenal. "That was our position; that is our position. Nothing has changed."
But for at least a day, the lid of pre-publication censorship imposed on Israeli journalists and academics eased a bit.
"Olmert made a mockery of the military censor, who threatens the media with trials and fines for merely hinting at what he announced," columnist Amir Oren wrote in a front-page commentary in the newspaper Haaretz.
Researchers trying to chronicle the nuclear program repeatedly have run afoul of the Defense Ministry's security and censorship office.
After a futile legal battle with the office, Israeli-American historian Avner Cohen gave up his research in Israel in 1995 and moved to the United States to finish writing "Israel and the Bomb." The groundbreaking book, based on declassified documents and interviews with former officials, revealed how Israeli technicians assembled two nuclear devices on the eve of the Middle East War of 1967.
Returning voluntarily to Israel in 2001, Cohen underwent weeks of interrogation by the censorship office about his sources.
Mordechai Vanunu, a former nuclear technician who served an 18-year sentence for his disclosure of Israeli nuclear secrets to a British newspaper, said he hoped Olmert's comment was "the beginning of a policy change" that will lead Israel to openly acknowledge its arsenal.
"Israel has invested enormous resources to prevent leaks and punish anyone who jeopardizes its 'ambiguity' regime," Bergman wrote in his analysis. "However, in the course of the years, this 'ambiguity' became virtual. It is absurd: Any child today can carry out a simple search with Google and find foreign publications that ostensibly reveal Israel's holiest secret."
Times staff writer Alissa J. Rubin in Paris contributed to this report.