James Schlesinger, who led the US Defense Department from 1973 to 1975, made the remark at a Pentagon news conference, after presenting a blue-ribbon panel report finding that US nuclear deterrence has slipped due to neglect in past years at high levels of the Pentagon.
Schlesinger, who served under presidents Richard Nixon and Gerald Ford, said North Korea probably has come to believe it is "reasonably safe from a nuclear response" because of the US response to its development of nuclear weapons.
But asked whether Iran feared a US nuclear attack, Schlesinger said, "I think they would regard that as a much more likely development.
"As you may recall in the recent democratic primaries, Mrs Clinton observed, 'We can obliterate you','" he said,
Noting that Clinton will be secretary of state in President-elect Barak Obama's administration, Schlesinger added, "I don't think that remark will be forgotten in Tehran, even if it is forgotten in this country."
Clinton made the remark in a US television interview in April, during which she was asked what she would do as president if Iran were to launch a nuclear attack on Israel.
"I want the Iranians to know that if I'm the president, we will attack Iran," Clinton said.
Obama, Clinton's rival for the Democratic nomination and now soon-to-be her boss, sharply criticized the New York senator at the time for the same sort of "bluster and saber-rattling and tough talk" that characterized President George W. Bush.
Meantime, Obama on Friday renewed his call for dialogue with Tehran, stressing that Washington must be "willing to initiate diplomacy" with the Islamic Republic.
"With respect to Iran, I'll have more to say about Iran after January 20. I have said in the past during the course of the campaign that Iran is a genuine threat to US national security," Obama said during a press conference on Friday in which he announced his picks for the administration's two top intelligence posts.
"But I have also said that we should be willing to initiate diplomacy as a mechanism to achieve our national security goals."
Obama said his national security team - reflective of his practical, pragmatic approach of diplomacy - has a policy towards Iran which will be released soon.
"When we have a policy towards Iran that has been shaped by my national security team, we will release it," Obama said.
A US attack on the Syrian village of Sukkariyah on October 26, has raised speculation about the likelihood of a US unilateral strike on the Islamic Republic.
Speculation that Israel could also bomb Iran mounted after a big Israeli air drill in June. In the first week of June, 100 Israeli F-16 and F-15 fighters reportedly took part in an exercise over the eastern Mediterranean and Greece, which was interpreted as a dress rehearsal for a possible attack on Iran's nuclear installations.
Israel and its close ally the United States accuse Iran of seeking a nuclear weapon, while they have never presented any corroborative document to substantiate their allegations. Both Washington and Tel Aviv possess advanced weapons of mass destruction, including nuclear warheads.
Iran vehemently denies the charges, insisting that its nuclear program is for peaceful purposes only. Tehran stresses that the country has always pursued a civilian path to provide power to the growing number of Iranian population, whose fossil fuel would eventually run dry.
Iran has warned that it would target Israel and its worldwide interests in case it comes under attack by the Tel Aviv.
The United States has always stressed that military action is a main option for the White House to deter Iran's progress in the field of nuclear technology.
Iran has warned that in case of an attack by either the US or Israel, it will target 32 American bases in the Middle East and close the strategic Strait of Hormoz.
An estimated 40 percent of the world's oil supply passes through the waterway.
Meantime, a recent study by the Institute for Science and International Security (ISIS), a prestigious American think tank, has found that a military strike on Iran's nuclear facilities "is unlikely" to delay the country's program.
In a Sep. 11 report, the Washington Institute for the Near East Policy also said that in the two decades since the Iran-Iraq War, the Islamic Republic has excelled in naval capabilities and is able to wage unique asymmetric warfare against larger naval forces.
According to the report, the Islamic Revolutionary Guards Corps Navy (IRGCN) has been transformed into a highly motivated, well-equipped, and well-financed force and is effectively in control of the world's oil lifeline, the Strait of Hormuz.
The study says that if Washington takes military action against the Islamic Republic, the scale of Iran's response would likely be proportional to the scale of the damage inflicted on Iranian assets.
Intensified threats by Tel Aviv and Washington of military action against Iran contradict a recent report by 16 US intelligence bodies which endorsed the civilian nature of Iran's nuclear plans and activities.
Following the US National Intelligence Estimate (NIE) and similar reports by the IAEA head - one in November and the other one in February - which praised Iran's truthfulness about key aspects of its past nuclear activities and announced settlement of outstanding issues with Tehran, any effort to impose further sanctions or launch military attack on Iran seems to be completely irrational.
The February report by the UN nuclear watchdog, the International Atomic Energy Agency, praised Iran's cooperation in clearing up all of the past questions over its nuclear program, vindicating Iran's nuclear program and leaving no justification for any new UN sanctions.
The UN nuclear watchdog has also carried out at least 14 surprise inspections of Iran's nuclear sites so far, but found nothing to support West's allegations.
Following the said reports by the US and international bodies, many world states have called the UN Security Council pressure against Tehran unjustified, demanding that Iran's case be normalized and returned from the UNSC to the IAEA.