September in New York. In the coming days, concrete blocks will be placed around the Waldorf Astoria, Intercontinental and other hotels, along with metal detectors and scanners at their entrances. Barricades will be erected to redirect pedestrian and vehicular traffic. Heightened security is part of the annual ritual to welcome government leaders and their entourages from around the world for the UN General Assembly opening session.This ritual has become just as ordinary as the end of summer over Labor Day weekend and the start of a new school year. New Yorkers, traditionally a resilient population, will go about their daily business and endure the additional inconveniences associated with living and working in a city that hosts UN headquarters.Yet, most will not heed what these visiting foreign leaders say from the UN podium. That’s too bad. Several of these heads of state are downright evil. Were it not for US commitments to international law, their planes might be prohibited from landing at Kennedy Airport.Which brings us to another September ritual: the visit of Iranian President Mahmoud Ahmadinejad. While attention for much of this year has been diverted to other hot spots in the Middle East, the Iranian leader is just as dangerous as ever.Lest anyone forget, while hosting Iran’s annual Jerusalem Day event last week, at the end of Ramadan, Ahmadinejad again called for the eradication of Israel. Iran would “never ever withdraw from this standpoint and policy,” he declared.Persistent threats against another UN member-state should prompt automatic outrage and condemnation. But instead of reprimanding Iran, the world body remains silent as it prepares to welcome him as it will any other head of state coming to UN headquarters.President Ahmadinejad this year will have the opportunity to address the world at least twice. Once at the General Assembly and a second time at the tenth anniversary of the infamous UN World Conference on Racism, first held in Durban in 2001. At the 2009 Durban Review Conference in Geneva, Ahmadinejad spewed his venomous attacks, denying the Holocaust and Israel’s right to exist. Precious few walked out and, worse, most applauded.THAT ALONE should raise concerns about Ahmadinejad’s upcoming New York visit. But that’s not all. The Iranian regime has ignored the international community’s entreaties to desist from pursuing its nuclear program, including four UN Security Council resolutions, economic sanctions by the US, EU and other countries, and appeals from the International Atomic Energy Agency (IAEA), which released on Friday its latest and perhaps most damning report of Iranian intentions.A year ago, Arab countries, notably Egypt and Saudi Arabia, as well as other GCC members, were expressing concerns about the looming Iranian nuclear threat. It seemed, momentarily, that these Arab nations and Israel shared a common view of Iran.Those worries have been pushed aside by the dramatic upheavals across the Arab world. As Egypt and others look inward to focus on developing new governments, hopefully democracies, following the overthrow of their own longtime despots, the ever-present Iranian threat has become a less urgent priority.The Iranians, of course, have not refrained from attempting to take advantage of instability in the region. From supporting Syria’s Bashar Assad, to supplying Hamas and Hizbullah, to meddling in Iraq and Bahrain, Iran continues to assert itself in ways that are harmful to peace and security.IAEA Director Yukia Amano is increasingly frustrated with Iran, a grave concern he shared in an interview with The Washington Post earlier this year. Since he assumed the position of IAEA director last year, the organization has come to accept the view that Iran is set on building a nuclear weapon.The clarity of that threat is set forth in the new IAEA report. Strongly criticizing Iran for failing to provide information about its nuclear activities, the IAEA warns that Iran may already have enough enriched uranium to produce four nuclear weapons. Coupled with media reports that Iran has taken additional measures to protect its nuclear program from cyber attacks as well as military actions, the likelihood that Iran will indeed test a device is becoming a grim reality.“We remain committed to preventing Iran from acquiring nuclear weapons,” President Barack Obama declared in a May speech in Washington. Unfortunately, the Security Council, which last adopted a resolution on Iran in June 2010, seems unlikely to take further action. It can’t even come together on Syria.Ahmadinejad’s arrival in New York constitutes another display of mockery of the international system. An Iran with nuclear weapons capability will pose new perils to Iran’s immediate neighbors, to countries within range of Iranian missiles – and beyond, if Iran transfers that technology to terrorist organizations or similarly hostile countries.If there ever was a clear and present danger to global security, an unchecked Iran intent on building nuclear weapons is it.The writer is the American Jewish Committee’s director of media relations.