TEHRAN, Iran – Iran’s chief nuclear negotiator, a relative moderate who struggled fiercely against the uncompromising agenda of President Mahmoud Ahmadinejad, has resigned his high-profile post, government officials announced Saturday.

The resignation of Ali Larijani dealt a major setback to Iranian moderates trying to forge a compromise over Iran’s pursuit of nuclear technology, which strongly is opposed by the West.

For two years, Larijani had served as secretary of the powerful Supreme National Security Council, which advises the highest levels of the Iranian government on key matters of state.

His withdrawal from the scene “may make negotiations even more problematic than in recent months,” said Patrick Cronin, a nuclear nonproliferation expert at the Institute for International and Strategic Studies, a British think tank.

Larijani, scion of a powerful clerical family and a confidant to Supreme Leader Ali Khamenei, is said to oppose Iran’s isolation over its insistence on enriching uranium. Insiders said he advocated cutting a deal with the West to end the crisis, which has led to two sets of economic sanctions against Iran.

Within Iran’s inscrutable inner leadership circle, Larijani was often at odds with Ahmadinejad, who refused to tone down his rhetoric or steer a more moderate course on the Islamic Republic’s nuclear ambitions.

“The difference between Ali Larijani and President Ahmadinejad was on the cost of the nuclear issue,” said an adviser to Larijani, who spoke on condition of anonymity. “Ahmadinejad insists on not any inch of compromise.”

Word of Larijani’s resignation came a few days after Russian President Vladimir V. Putin arrived in Tehran, the Iranian capital, and proposed a deal to end the nuclear stalemate, and just before Larijani was to have discussed the issue with European Union foreign policy chief Javier Solana.

“We will consider what you said and your proposal,” Khamenei reportedly told Putin, according to the official IRNA news agency, before adding: “We are determined to satisfy the needs of the country in nuclear energy, and it is for this that we take seriously the question of enrichment.”

Analysts said the resignation probably signified that Iran’s leadership had opted to reject Putin’s proposal, which most observers say was a deal in which Iran would halt its uranium-enrichment program in exchange for concessions from the West.

“Mr. Ali Larijani believed in a sort of compromise on uranium enrichment, but President Ahmadinejad thinks that Iran should go ahead with the current uranium enrichment and current nuclear policy,” said Sadegh Zibakalam, a professor of political science at Tehran University. “Therefore, Mr. Ali Larijani had no option but to resign.”

Enriched uranium can be used to power electricity plants or, if highly concentrated, become explosive material for an atomic bomb. President Bush has said Iran should not have the know-how to create such a weapon. The U.N. Security Council has demanded that Iran halt enrichment until questions about its past nuclear activities are cleared up.

The West, led by the U.S., accuses Iran of using a legal nuclear energy program to mask an illegal pursuit of nuclear weapons technologies. Iran insists that its nuclear program is meant only to generate electricity.

Reacting to the resignation, White House spokeswoman Eryn Witcher said, “We seek a diplomatic solution to the issue of Iran’s nuclear program and hope that whomever has this position will help lead Iran down a path of compliance with their U.N. Security Council obligations.”

Since taking up his post more than two years ago, Larijani had repeatedly tried to tender his resignation in frustration over Ahmadinejad’s harsh rhetoric.

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“Larijani had resigned several times, and President Mahmoud Ahmadinejad finally accepted his resignation,” government spokesman Gholamhossein Elham said Saturday at his weekly news briefing, IRNA reported.

Elham played down the resignation, saying that Iran’s nuclear policies would not change and that Larijani resigned for personal reasons to pursue other political activities. But one former adviser to the Iranian government on the nuclear issue said that “the gap between him and Ahmadinejad had reached a point that he simply had to resign.”

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Larijani has long been considered a relatively moderate voice. In 2005 he pushed for a two-year suspension of Iran’s enrichment program, and this year he played a key role in defusing a crisis that erupted when Iranians seized a group of British sailors and Marines in disputed Persian Gulf waters off the coast of southern Iraq.

Diplomats say Larijani had developed a fruitful line of communication with Solana, the EU point person on Iran’s nuclear issue.

Some analysts pointed out that style rather than substance characterized the differences between the two camps on the nuclear issue.

“Larijani was not advocating making major nuclear compromises, but he appreciated the need to retain constructive dialogue with the EU and felt Ahmadinejad needlessly undermined Iran’s case with his blusterous rhetoric,” said Karim Sadjadpour, an Iran expert at the Carnegie Endowment for International Peace, a Washington, D.C., think tank.

Replacing Larijani with Saeed Jalili, Iran’s deputy foreign minister for European and U.S. affairs, buys Iran more time to pursue its ultimate goal of becoming a nuclear power, said Saeed Leylaz, an Iranian analyst and economist.

“The Islamic Republic of Iran is in a race against time with the West,” Leylaz said. “All in all, Iran is going toward more radicalization and full nuclear power.”

He said Iran’s leadership, watching oil hover near $90 a barrel, thought it had little to lose by taking a tough stance, convinced that the U.S. wouldn’t dare launch a military attack against Iran and risk sending the world economy into a recession.

Special correspondent Mostaghim reported from Tehran and Times staff writer Daragahi from Amman, Jordan. Times staff writer Alan C. Miller in Washington, D.C., contributed to this report.

AP-NY-10-20-07 1717EDT

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