Aimed -- it seems -- at keeping America's attention firmly on the unacceptable danger of Iran building nuclear weapons, Prime Minister Benjamin Netanyahu and Defense Minister Ehud Barak are hinting that an Israeli attack on Iran could come at any time.

Officials in Jerusalem and in Washington have suggested, however, that they believe Netanyahu has been privately asked by President Barack Obama not to attack until after America's election day; and many Israeli strategic analysts believe that a military strike can indeed wait until then. However, Netanyahu is trying to maintain the pressure, not only on Iran but on the United States, by declaring that time is running out for a peaceful solution. He barely conceals the fact that he would prefer that the U.S. carry out the attack on Iran.

The prime minister is not saying publicly that Israel's foreign espionage and operations agency -- the Mossad -- is highly active, day and night; and its main focus, for eight years now, has been Iran's nuclear program. The agency's director from 2002 through 2010, Meir Dagan, made a point of redirecting the Mossad's priorities: with a lot less emphasis on Palestinian politics and militant groups, and a laser beam of attention on Iran.

We reported last month that at least four assassinations of Iranian nuclear scientists in Tehran were carried out by Mossad operatives. The Israeli attackers were part of an elite unit within Israeli intelligence, called Kidon (the Hebrew word for Bayonet). Since its creation, in the wake of the Palestinian terrorist attack that killed 11 Israeli athletes at the Munich Olympics in 1972, many espionage experts have concluded that Israel's assassins respect no rules and know no boundaries.

We've learned, however, that the Kidon unit does respect an unwritten regulation adopted by Israel's secret agencies about half a century ago: not to use local Jews as spies or saboteurs in their home countries. This is relevant consideration in Iran, where around 25,000 Jews live -- long after most moved away in the wake of the Islamic Revolution of 1979.

The restriction is somewhat ironic, because Israeli secret agents have devoted a lot of their energies to protecting or rescuing Jews. Intelligence agency chiefs have always felt obliged to be guardians of their brethren, far and wide. Two units of Israel's intelligence community -- Nativ, which specialized in helping Soviet Jews, and Bitzur, part of the Mossad -- organized Hebrew education, self-defense, and secret emigration to Israel. The Israelis learned -- at a painful cost of seeing Jews tortured and executed in Egypt and Iraq in the 1950's -- not to use local Jews as spies inside what the Mossad calls "target countries."

In Iraq, in late 1951, around one hundred Jews who had agreed to spy for Israel were arrested -- and two were hanged. In Egypt, dozens of young Jews -- involved in an Israeli sabotage campaign aimed at humiliating then-President Gamal abdel Nasser -- were rounded up in 1954. Two members of the group were hanged, and six others were given harsh prison sentences. An Israeli intelligence officer, Max Bennett, committed suicide in an Egyptian jail cell. In any Arab country where Jewish citizens were accused of spying for Israel, life quickly became intolerable for the entire Jewish community.

The Mossad felt that this applied to every nation on earth, not only Arab lands, and agency directors decided to avoid putting local Jews in sensitive situations anywhere. There were minor exceptions: A Jew might be used for a little bit of logistical advice or assistance -- a low-level relationship which the Israelis referred to as being a sayan ("helper") -- but never to act as an agent or a spy in their own home country.

There was one glaring violation of the rule, and it has roiled United States-Israel relations for 27 years: the arrest in Washington of Jonathan Jay Pollard, a civilian who abused his job in U.S. Naval Intelligence to procure secret documents for Israeli handlers. It turned out that the Mossad did not run Pollard. He had offered his services to an Israeli military officer, and it was a special unit of the defense ministry in Tel Aviv that accepted Pollard's offer.

The head of that unit, known as Lakam (a Hebrew acronym for Science Liaison Bureau), was Rafi Eitan, an unusually adventurous Israel intelligence operative whose career included the capture of Nazi war criminal Adolf Eichmann in Argentina in 1960.

Eitan gambled, by running an American Jew as a spy; and it was the American spy who lost. Pollard was sentenced to life in prison. Other American Jews working in the defense and intelligence fields immediately found themselves under suspicion of disloyalty.

The bitter Pollard experience only strengthened the Mossad's resolve not to use Jewish locals as spies. Thus the agency carefully avoids contact with Jews living in Iran. Yet Israeli officials say privately that they will continue to act in innovative, secret ways against Iran's nuclear program -- because that is far preferable to having all-out war break out.

Dan Raviv, a CBS News correspondent based in Washington, and Yossi Melman, an Israeli journalist specializing in security issues, have co-authored five books, including the new Spies Against Armageddon: Inside Israel's Secret Wars. They blog at IsraelSpy.com.