Even as the European Union reports that international sanctions will not prevent Iran from making a nuclear bomb, the West is opting for slow-moving diplomacy.

It is important to pay special attention to two factors that call for a more urgent response — the apocalyptic religious motivation of Iran’s decision makers and the proximity of Iran to reaching its nuclear goal.

President Ahmadinejad concluded his speech at the United Nations on September 17, 2005, with a prayer, “O mighty Lord I pray to you to hasten the emergence of your last repository, the promised one, that perfect and pure human being, the one that fills this world with justice and peace.”

The “perfect being ” that Mr. Ahmadinejad referred to is the “absent mahdi” — the 12th imam, son of Hasan, who, according to Shiite tradition was hidden as a child in the 10th century. According to this tradition, the 12th imam will reappear to establish justice in the world after an imminent war of Gog and Magog that is accompanied by suffering, bloodshed, and martyrdom. Afterwards, Shiites — today only 15% of the Islamic world — believe they will overcome the Sunnis and Islam will rule the globe.

The belief in the return of the mahdi, which resembles messianic Judaism and Christianity, would not be so threatening, were it not for the phenomenon of movements which see the mahdi’s return as materializing through the divinely assisted efforts of the faithful.

Most dangerous today is the emergence of secret religious action groups committed to fulfilling the conditions for the mahdi’s return. They receive their instructions through mediums, whose identities are secret, and who are said to maintain contact with the mahdi through dreams.

There are reliable testimonies that the president of the Iranian Atomic Agency since 1997, Gholamreza Aghazadeh, is a longstanding member of one of these groups. He regards his work as a holy mission and has mobilized his organization to gain uranium and plutonium production technologies in order to hasten the mahdi’s return.

Of greater concern is Mr. Ahmadinejad’s connection with the mahdist movements. The leader of one such movement, Ayatollah Masbah Yazdi, the only ayatollah that supported him in the presidential election, is his patron. His other supporters are the veteran commanders of the Revolutionary Guard that fought the Iran-Iraq war, some of whom attribute their victories to the direct intervention of the mahdi.

Confirmation of the dangerous posture of this power group was revealed in a classified letter from Ayatollah Khomeini to the mullahs of Qom published in October 2006 by the former president and opponent of Mr. Ahmadinejad, Ali Akbar Hashemi Rafsanjani. Ayatollah Khomeini said he ended the war because the Revolutionary Guard commanders were determined to continue it and had requested launching a five-year crash program of nuclear weapons development.

These Revolutionary Guard commanders also engage in incitement against Jews and Christians. By Western standards, Mr. Ahmadinejad and his group are irrational, as they follow the capricious mahdi intermediaries, who are unknown, unpredictable, and ready for personal and national martyrdom.

Yet there are other Iranians with “rational” strategic motivations for wanting to go nuclear, such as national pride, acquiring regional influence, and securing immunity for the Islamic regime. Consequently, Mr. Ahmadinejad’s nuclear policy has won wide support in Iran, including of Ayatollah Ali Khamenei, as well as of various conservative religious leaders and even of political figures considered reformists.

Equally worrisome as the motivation of the Iranian leadership is Iran’s rapid technical development of nuclear capability. The timetable estimates of monitoring and intelligence agencies are based on what they can see and monitor as well as on technical estimates of the rate of uranium enrichment in Iran’s operative centrifuges. On the basis of open information, experts reckon the minimum time period for reaching the point-of-no-return is between three and five years.

Contrary to these experts, who failed to discover the Libyan nuclear project, there are testimonies and estimates, by Iranian scientists working on the nuclear project and recently even by Iranian officials, of a timescale on the order of months. These estimates are based not only on the conduct and statements of Mr. Ahmadinejad, but also on evidence that there is a parallel nuclear developmental effort under the auspices of the Revolutionary Guard. The Iranians admitted purchasing the blueprints of isotope separation centrifuges as early as 1987. There are testimonies and even scientific publications by Iranian scientists that prove that plutonium technology has been developing there for almost 20 years.

This technology is useful only for weapons production, and is the same as that used by the North Koreans, Iran’s partners in strategic weapons development for the last 15 years. It has been even reported that Iranian scientists participated in the North Korean nuclear test in October 2006. Therefore, it would be negligent to dismiss the possibility that Iran has secretly reached, or is close to achieving, mastery of nuclear weapons production.

Clearly, the combination of these two very troubling factors — fanatic motivation and nuclear capability — poses a great danger to world peace and constitutes an existential threat for Israel. Even if Mr. Ahmadinejad and his group do not use their weapon right away because of opposition from senior ayatollahs and pragmatist clerics, he will not hesitate to advance the ideology of Shiite dominance. This policy of aggression may lead to a nuclear war within a period of a few years. If Iran’s zealot leaders do not start a nuclear war, a threatened Israel might be pushed to make a pre-emptive attack.

The more optimistic scenario that sees the pragmatist faction in the Iranian regime gaining the upper hand is still very dangerous. The pragmatists could hardly be expected to abolish nuclear weaponry, which ensures Iran the status of a local superpower. Under the guise of being able to threaten a nuclear strike if attacked, Iran would continue to build up its nuclear arsenal to a level of serious strategic threat to Israel and other Middle East states. It would use its proxies in Iraq, Lebanon, Palestine, and Syria and terrorist groups all over the world to expand its control and threaten the main oil resources of the world. Moreover, Sunni Arab countries would then most likely launch nuclear weapons development programs of their own.

The decision of how to deal with Iran cannot be postponed for years. A default “ignore and wait” nonaction policy would be of immense consequence. And letting Iran reach the nuclear armed status of North Korea would prove to be a bitter historic mistake.

On the positive side, there are some signs that the more responsible opposition still has some power in Iran. In December 2006, Mr. Rafsanjani — the more pragmatic conservative opposition rival of Mr. Ahmadinejad — was elected as the head of the “experts Committee,” which was formed to select the next supreme leader. The Yazdi faction got only five delegates out of the 86 elected. In January 2007, 150 of the 260 members of the Iranian Parliament signed a petition against Mr. Ahmadinejad deploring his economic failures and radical rhetoric. A rift is forming between Mr. Ahmadinejad’s power group and the pragmatic clerics, both conservative and reformists. These developments may be the result of the tougher stand recently taken by America.

Certainly, the increased military pressure by America must be kept up. The intensive engagement of America and its allies in support of opposition groups representing pro-American segments of the Iranian population is also called for in order to topple the regime. High intensity propaganda like the effective operation of Voice of America beyond the Iron Curtain, broadcasting from Iraq’s long borders and satellites, as well as clandestine intervention, may also help strengthen the internal opposition. But stronger measures will probably be required to bring down the regime and prevent the nuclearization of Iran.

The author, an Iranian scientist, writes without a byline for security reasons.