For European and American leaders, U.N. General Assembly debates would not be the complete without delivering a full-throated attack on Iran's nuclear program.

But this year, the council's major powers have been mute, particularly the three European powers, Britain, France and Germany, that have engaged in a long, fruitless effort to persuade the Iranian leadership to provide verifiable assurances that its nuclear program is peaceful in exchange for a basket of trade benefits and political rewards.

France's President Nicolas Sarkozy didn't make a single reference to Iran's nuclear program in his address last week to the General Assembly. British Prime Minister David Cameron blasted Iran's repressive policies at home, but said nothing about its atomic ambitions. Ditto for Germany's Foreign Minister Guido Westerwelle.

Minutes after Iranian President Mahmoud Ahmadenijad blasted the United States, Britain, and Israel for military aggression in the Middle East and elsewhere, Cameron shot back: "He didn't remind us that he runs a country where they may have election of a sort but they also repress freedom of speech, do everything they can to avoid the accountability of a free media, violently repress demonstrations and detain and torture those who argue for a better future."

President Barack Obama did commit a couple of sentences to Tehran's nuclear program, but it was largely boilerplate, and lacked the sense of urgency and alarm that has marked previous public statements.

"The Iranian government cannot demonstrate that its program is peaceful, it has not met its obligations and it rejects offers that would provide it with peaceful nuclear power," Obama said in a U.N. speech that addressed the Arab Spring and the Palestinian-Israeli conflict. Iran, along with North Korea, "must be met with greater pressure and isolation," he said, if they "continue down a path that is outside international law."

If one missed the fire and brimstone diplomatic sermons on Iran's nuclear threat that used to be standard fare in Washington and Paris there was only Israeli Prime Minister Benjamin Netanyahu. 

Speaking a day after Ahmadinejad excoriated the West for a litany of historical sins, Netanyahu said "can you imagine that man who ranted yesterday -- can you imagine him armed with nuclear weapons? The international community must stop Iran before it's too late. If Iran is not stopped, we will all face the specter of nuclear terrorism, and the Arab Spring could soon become an Iranian Winter."

But apart from Netanyahu, it was notably quiet. "Most Council members remain concerned about the continuation and possible acceleration of Iran's nuclear program," according to an assessment by the Security Council Report, a non-profit, Columbia University-affiliated research group that tracks the Security Council's activities. "However, as has been the case for some months, even members willing to consider additional action against Iran do not view any new measures as likely in the near future. It appears most members are not eager to push for additional Council action at this time." 

Certainly, Iran's nuclear program hasn't gone away or halted its advances.  On Sept. 2, the International Atomic Energy Agency (IAEA) issued a mixed report on Iran's nuclear activities, citing continued cooperation with nuclear inspectors who visited many of Iran's declared nuclear facilities, but also confirmed efforts by Tehran to step up its uranium enrichment activities -- including the introduction of more advanced enrichment technology -- in flagrant violation of successive U.N. resolutions.

The report also cited "extensive and comprehensive" information related to a possible clandestine military program to develop a nuclear payload for a missile. The report's findings, coupled with Iranian officials' public pronouncements, has raised concerns among the U.S. and Europeans about Iran's plan to expand their stockpile of a more refined grade of uranium enriched to 19.75 percent -- higher than that needed for the generation of electricity and more than required to fuel its advanced medical reactor in Tehran.

For its part, Tehran has repeatedly denied it is pursuing a nuclear weapon, saying it is pursuing a peaceful nuclear energy program. Last week, Ahmadinejad said Iran's leadership considers nuclear weapons program's "evil" and wants no part of it.

Ahmadinejad proposed last week in an interview with the Washington Post's Lally Weymouth, to halt Iran's enrichment of the higher-grade 19.75 grade uranium if the United States or some other country would supply Iran with a reliable supply of the enriched uranium, which is used in a medical reactor that produces anti-cancer treatment, but could potentially converted into weapons-grade fuel -- which must be enriched to 90 percent.

The United States and other Western governments have not formally responded to the offer, which they say has previously been proposed in bad faith by the Iranian leadership to avoid charges of intransigence.

David Albright and Christina Walrond of the Institute for Science and International Security outlined a range of projections on how long it would take Iran to acquire a large enough stockpile of 19.75 percent-grade fuel (also known as low-enriched uranium, or LEU) needed for the conversion into a nuclear-weapons grade fuel.

"The mid-projection, or the rate Iran seeks, estimates that by November 2012, Iran could have accumulated more than enough 19.75 percent low enriched uranium so that after further enrichment it would have enough weapons grade uranium for about one nuclear weapon," they wrote. "The worst case scenario is that by mid-2012 Iran would have enough 19.75 percent LEU for a nuclear weapon. The least worrisome case is that Iran would need until late 2013 to accumulate enough 19.75 percent LEU for a weapon."

The time table doesn't mean that they will be able to produce or deploy  a nuclear weapon in 2013. There are still substantial technological hurdles Iran would have to cross -- including mastering the conversion of nuclear fuel into a highly enriched grade and loading it into a workable missile. And any move to weaponize its nuclear fuel would require the expulsion of IAEA inspectors, a move that would heighten international political pressure on Tehran, and potentially trigger a military response.

France's U.N. envoy, Gerard Araud, acknowledged in a public discussion that I moderated on Tuesday at the French Consulate in New York, that the nuclear problem has fallen "under the radar screen" -- even as Iran's nuclear program appears to be moving slowly, but inexorably, towards the capacity of developing a nuclear weapon, and toward a likely military confrontation with the West.

Araud, who has been directly involved in nuclear negotiations with Iran for more than eight years, initially as France's political director and more recently as its U.N. ambassador, said that the U.N. Security Council has been preoccupied with responding to the political fallout brought out about Arab Spring. "The international community doesn't know to chew gum and walk at the same time," he said.

Araud also said that four rounds of U.N. sanctions are moving closer to harming the "crucial, vital interests" of Iran's trading partners, mostly notably Russia and China, the latter of which is becoming increasingly dependent on Iranian oil to meet the energy needs of a rapidly growing economy. But the Western sanctions effort has become more complicated by the presence of three non-permanent Security Council members -- Brazil, India and South Africa -- that share Chinese and Russian opposition to sanctions.

"Is it possible to still tighten sanctions? Is it possible to go further, to move further?" he asked. I doubt it. I really doubt it. Maybe in six months."

The French envoy said that the existing U.N., U.S., and European sanctions, combined with what appear to be covert sabotage efforts directed at Iran's nuclear program, are raising the costs for the Iranian leadership for defying repeated resolutions demanding they halt their enrichment activities. They have also hampered Iran's ability to shop around the world for essential parts for its nuclear program. Indeed, the last year has seen a marked increase in the number of seizures of foreign vessels engaging in illicit trade with Iran.

"I think it's too easy to say [the sanctions] are not working because the Iranians have not stopped" enriching uranium, said Araud. "We consider that they are effective; that they are hurting the economy."

But he conceded that efforts to restart the stalled diplomatic process have foundered, largely as a result of Iranian intransigence, and he dismissed Ahmadinejad's latest offer as insincere. "Frankly we have tried everything," he said. "They have never shown any openness...to a substantial negotiation."

Araud said the lack of a meaningful diplomatic process has inherent risks that may inevitably lead to a military confrontation.

"If we don't succeed to open the negotiations with the Iranians there is a strong risk of a military option and we want to avoid it because a military option would have disastrous consequences on the short and medium and long term in this part of the world."

Araud, who previously served as France ambassador to Israel, challenged Israel's contention that Iran's leadership is bent on the destruction of Israel, saying he believes their true goal is projecting power and influence throughout the wider region, which would insulate them from the threat of an overwhelmingly superior U.S. military threat.

"I think the Iranians are pretty rational; they are extremely rational," he said, noting that a nuclear strike against nuclear-armed Israel "would be mutually agreed destruction. You don't risk destruction to make a point."

Araud said that he would assign the likelihood that Iranian nuclear would never launch an atomic attack against Israel at 99.9 percent, but that "if you are on the side of Israel you don't run the risk. This one percent is too expensive, you can't afford it."

Follow me on Twitter @columlynch