NEW YORK — As Iranian President Hassan Rouhani prepared to address the UN General Assembly on Thursday, the US Holocaust Memorial Museum pressed world leaders to condemn Tehran’s history of promoting Holocaust denial and pressure its leadership to recognize the reality of the genocide.

“We want to make sure that the upcoming discussions at the United Nations is informed by facts about official attempts to promote hatred and extremism in the form of Holocaust denial,” Ted Stahnke, the director of the museum’s Initiative on Holocaust Denial and Antisemitism said Tuesday.

“The museum calls on international leaders at the General Assembly to condemn [Iran’s] Holocaust distortion.”

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Delineated in a timeline on the museum’s website, Tehran’s history of denying Nazi Germany’s systematic murder of more than six million Jews goes back to Al-Quds Day 1998 — when then president of Iran, Ali Akbar Hashemi Rafsanjani, dismissed that historical event as “Zionist propaganda.”

Most recently, there was a Holocaust-themed cartoon contest this past May that mocked the Nazi massacre. State Department spokesman Mark Toner said the US was concerned the exhibition was being used as “a platform for Holocaust denial and revisionism and egregiously anti-Semitic speech, as it has in the past.”

Foreign Minister Zarif has been questioned on the episode, but has on numerous times asserted the contest was hosted by an NGO and not the Iranian government.

On a call with reporters Tuesday, Stahnke and Maziar Bahari, an Iranian filmmaker and activist, noted that Rouhani’s Thursday speech will be his first at the UN and in the United States since that incident.

They also issued warnings against those who might claim both Rouhani and Zarif are moderate reformers, and that while Holocaust denial in Iran does not emanate from the regime in Tehran.

People “think they can say, ‘The government of Iran has not denied the Holocaust,’ but that is a lie,” Bahari said, before he offered an explanation for the Iranian political dynamic at play.

“Holocaust denial and anti-Semitism has become a weapon of the hardliners in Iran to use against reformers,” he said. “So whenever the hardliners want to put pressure on reformers they promote anti-Semitism and deny the Holocaust because they know exactly what it will mean from outside of Tehran.”

Based on previous UN speeches Rouhani has given and a recent op-ed by Iranian foreign minister Mohammad Javad Zarif, Stahkne predicted Iran’s head of government will use the forum to denounce extremism while taking aim at regional rival Saudi Arabia.

However, the campaign is hoping to steer the conversation out of Iran’s hands.

“Iranian leaders should be made to talk about Iranian Holocaust denial at the UN General Assembly,” Bahari said.