President Hassan Rouhani at the United Nations General Assembly last year. This year, he will say that Iran’s government is peaceful and will lie about atrocities committed against its people.

The Iranian government has a choice to make when President Hassan Rouhani visits New York this month: It can either remain a backward regime led by fundamentalist clerics or it can become a legitimate member of the world community. I predict that President Rouhani will try to present a more rational image of his government in his speech, on 28 September, addressing the 193 countries of the United Nations General Assembly and in individual meetings with world leaders. He will highlight signing the nuclear deal with the United States and other world powers as proof that the Iranian government is modern and peaceful. But he and his diplomats will also lie about the atrocities they commit against their own people.

The best way to test the Iranian government’s will for a new chapter in its relationship with the rest of the world is to question them about their treatment of 300,000 Iranian Baha’is, the country’s largest religious minority. The Baha’is have been the most persecuted group of Iranians since the 1979 Islamic Revolution. As such, they should be viewed as the barometer of the government’s domestic and international policies. Every time a more liberal faction has come to power — such as when Mohammad Khatami, a moderate cleric, was elected president in 1997 — and has attempted to give more freedom to Iranians and to repair its international relations, the Baha’is have enjoyed a relative relief from persecution. But when the regime has curbed civil liberties and become hostile to other countries, such as after the rigged election in 2009, the first victims of the ensuing crackdowns have been the Baha’is.

The Baha’i Faith began in the 19th century and its fundamental beliefs are non-violence, universal education and equality. Baha’is believe that their prophet, Baha’u’llah, is the latest prophet of God. Ever since the faith was founded in Iran, the Baha’is have been persecuted by some Shia Muslims who call them heretics and corruptors of the earth — crimes punishable by death in Islam. The clerics have especially objected to two Baha’i beliefs: the equality of men and women and the idea that a clergy is not necessary for religious guidance. These beliefs threatened the patriarchal system of the clergy and its livelihood. In the 19th century, Baha’is were shackled and paraded in the streets of Iranian cities and their homes were burnt to the ground.

Iran’s government has persecuted the Baha’is in a more systematic fashion since the clerics came to power after the 1979 revolution. Hundreds were kidnapped or murdered in the early 1980s. Baha’is are barred from teaching and studying in universities. They can’t be employed legally, and their businesses, cemeteries and places of worship are regularly ransacked by vigilantes supported by government agents.

After an international, mostly American, outcry against the 1980s killings, Iran’s Supreme Leader, Ayatollah Ali Khamenei, ordered that the Baha’is “be tolerated” as citizens but denied their basic rights. In 2012, he issued a fatwa against the Baha’is, calling them “infidels” and “unclean.” He insisted that Muslims “should not touch the food or other Baha’i belongings that can sully Muslims.”

Hundreds of prisoners of conscience — including dozens of Baha’is — are unjustly held in Tehran’s infamous Evin Prison.

No one expects the Baha’is to be granted equal rights overnight — during President Rouhani’s visit to the United Nations — but the first step for Iran’s government to show real signs of change is to start talking about the ongoing persecution of 300,000 Baha’is.

When Iranian officials are asked to explain why they persecute the Baha’is, they simply don’t tell the truth. They claim that Baha’is are not discriminated against, and that those Baha’is who have been killed or imprisoned in Iran have been subjected to severe punishments for committing other crimes, mainly espionage, and not because of their faith. The Iranian government has not produced even a single document to prove that an Iranian Baha’i has spied for any country. You can be sure that if the Islamic regime had a shred of evidence they’d have spread it across their media outlets.

In recent conversations, such as one I had before writing this piece, pro-Rouhani Iranian officials claim they don’t condone the treatment of the Baha’is. “May God be my witness, if Mr. Rouhani had the power, he would’ve stopped all discriminations against the Baha’is,” a friendly Iranian foreign ministry official told me in a Skype call. “But this is not the right time to raise the Baha’i issue. We’re trying to convince our own radicals that this nuclear deal is an opportunity for Iran to have better relations with other countries, have a better economy and provide the basics for our people. We have more important priorities than the Baha’is now. We should talk about them and other problems when we have a calmer situation in Iran, and the region.”

I had to stop my friend before he continued. “Then, you mean, not in this lifetime?” I asked.

My friend hung up on me. But Iranian reformists have repeated this half-hearted line for twenty years. They have tried to make Iran a more inclusive country but they have failed to find the courage to address religious zealotry — the main reason behind the problems that have plagued Iran since the 1979 revolution.

President Rouhani now has a chance, on a global platform, to improve his government’s relationship with the rest of the world and his own people. It’s time for him and his government to start by explaining why they have systematically persecuted the Baha’is for almost forty years. Expecting an instant change of heart by Iranian officials is unrealistic — but if they told the truth about the suffering of 300,000 Iranian Baha’is, it would lead to constructive dialogue and point the way to true change.

Maziar Bahari is the founder of the notacrime.me/Iran campaign for freedom of expression and education equality in Iran. Archbishop Desmond Tutu and Dr Shirin Ebadi — both Nobel Peace Prize laureates — are two of the campaign’s biggest supporters. And this year the campaign is creating murals around the world (starting in New York City ahead of the United Nations General Assembly) to bring attention to Iran’s human rights crisis.