BRUSSELS, Belgium — In the United States and in Europe, there is a widespread belief that the Bush administration has failed to engage Iran diplomatically. Among the advisers to the Iraq Study Group, of which I was one, most believed that the Bush administration, not the mullahs' regime, was the most culpable party in foreclosing dialogue between Washington and Tehran after 9/11.

Iran's American-educated longtime ambassador to the United Nations, Javad Zarif, has tirelessly suggested that the administration missed opportunities for improving relations and is tone-deaf to his country's peaceful intentions.

Yet it ought to be clear that just the opposite is the case. The clerical regime today is no more interested in reaching a peaceful modus vivendi with the United States than it was in the 1990s, when President Clinton and Secretary of State Madeleine Albright all but begged President Mohammad Khatami of Iran to just talk to them.

Case in point: Haleh Esfandiari, an American citizen and the director of the Middle Eastern program at the Woodrow Wilson International Center for Scholars in Washington, has been jailed in Tehran's notorious Evin prison since May 8. For years, she has been an articulate and determined advocate of better relations between her homeland, Iran, and her adopted country.

Just as former U.S. Rep. Lee Hamilton, the head of the Wilson Center and co-chairman of the Iraq Study Group, has advocated a "diplomatic offensive" toward Tehran, Esfandiari has assiduously practiced micro-diplomatic soft power, using the Wilson Center as a bully pulpit for reconciliation. Suspicious, cynical, hawkish and religiously oriented analyses of the Islamic Republic — my school of thought — have not been commonly heard at the Wilson Center under Esfandiari and Hamilton.

In Iran, too, Hamilton and his Iraq Study Group co-chairman, James Baker, are seen as America's proponents of engagement. Esfandiari had traveled to Iran frequently in recent years and was, on a smaller scale, viewed in a similar way. By arresting her during a visit to her 93-year-old mother, the clerical regime sent a blatant message to Hamilton about the effectiveness of engagement. He responded with a private letter to President Mahmoud Ahmadinejad, asking him to allow her to leave the country. Instead, she is behind bars, described by Tehran as an agent of regime change, an "American-Zionist" spy.

It is undoubtedly the Hamilton connection and her marriage with an Iranian-born Jew — a sin under Islamic law for a Muslim woman — that made Esfandiari such an irresistible target for a regime fond of taking hostages to intimidate its enemies.

The clerical regime doesn't play fair: A 67-year-old woman who has over the years shown Iran's representatives in the United States and other visiting Iranians, including esteemed clerics, the utmost kindness and respect is a perfect target to show the regime's distaste for Iranians who want to build bridges.

Iran's Ministry of Intelligence, which has dueled with the Central Intelligence Agency for 20 years, knows the difference between real, on-the-payroll "traitors" and those the regime just dislikes and labels as spies. It undoubtedly knows Esfandiari isn't working on some regime-change plot masterminded by Langley or the Mossad.

Esfandiari's arrest is what you could call "clerical engagement": Iranians and Americans are meant to (re)learn that the ruling clergy exclusively defines the terms of engagement. "Mutual interest," something Hamilton repeatedly insists the United States and clerical Iran share, isn't a phrase I've seen used by Ali Khamenei, Iran's virulently anti-American and anti-Semitic ultimate leader. Hamilton and Baker raised the fearful (to the clerical regime) specter of an America eager to embrace the Islamic Republic. The mullahs, in a very personal, Iranian way, have replied.

Since the Germans and French first introduced the idea of "constructive engagement" with Tehran in the early 1990s, Iran has consistently checked any Western effort to have a meaningful "dialogue of civilizations." Little harmless things are possible — Western scholars attending academic conferences; Western-Iranian sporting events that the mullahs care little about — but nothing that challenges the regime's core beliefs and mission. The humbling of the United States remains the goal of Ayatollah Ruhollah Khomeini's children, who still see themselves as the vanguard of a militant Islamic world.

Since the summer of 1999, when Iran's reformist student movement was crushed by the security services, European investment in Iran has grown rapidly, by the tens of billions of dollars. As the money flows in, the clerical regime has harassed and murdered lay and clerical dissidents, exiling some of its most trenchant critics abroad or sending them to jail. Expanding commercial contacts, the Europeans had argued, was supposed to open up Iran and moderate its leadership. Baker and Hamilton, and much of the "realist" camp in the Democratic and Republican Parties, have essentially made the same argument.

The clerical regime, however, knows what Italian city-states and the Ottoman Empire knew well: You can trade with and concurrently try to vanquish your enemy. Europeans and many Americans are enraptured by the idea that commerce and capitalism make friends out of enemies, a view that conveniently allows one to spend less on defense and practice a more friendly foreign policy.

Advocates of engagement don't want to see that for Iran's ruling clergy there is no fundamental contradiction between seeking trade deals with Boeing and Exxon and also bombing American troops in Saudi Arabia, abetting the movement of al-Qaida's holy warriors (see the 9/11 commission report) and exporting explosive devises to Iraq to kill American and British soldiers.

Many Iranians feel ashamed about the Islamic revolution's violent excesses, which were particularly bad 25 years ago when I was a student of Esfandiari and her husband, Shaul Bakhash. However, the two never failed to point out the basic decency and beauty of their homeland and of the men and women who made the Iranian revolution. Now the revolution's ugliness has again pre-empted the country's goodness by brutalizing a woman who has done as much as any Persian poet to show Islamic Iran's complex, rich humanity.

It will be interesting to see whether Esfandiari's large network of moderate friends — Iranian scholars, ambassadors and clerics — can activate the traditional Persian way of posht-e pardeh, "politics behind the curtain," to free her. Evin is a terrible place to wait long.

As for the Western powers, they should recall that Ronald Reagan's finest moments came when he saw that the struggles of Soviet dissidents should be at the forefront of American-Soviet relations. The liberation of one individual should sometimes define a nation's foreign policy.

If the Europeans are wise, they'd ensure that no discussion with the Iranians on any subject occurred without highlighting the plight of Esfandiari. She indefatigably made European arguments about the need and effectiveness of soft power; they should just as indefatigably defend her.

Neither the Europeans nor the Americans will find any common ground with the clerical regime as long as Esfandiari languishes in prison. Until she is freed, it will remain clear that the regime understands nothing other than brute force.

Reuel Marc Gerecht, a former Central Intelligence Agency officer, is a resident fellow at the American Enterprise Institute. This commentary was written for The New York Times.