DUBAI (Reuters) - Islamic hardliners in Iran's parliament have summoned Foreign Minister Mohammad Javad Zarif over public comments condemning the Holocaust, the official news agency IRNA reported on Monday.

Zarif, who is also Iran's chief nuclear negotiator, caused an uproar among conservatives in Iran when he called the Holocaust a "horrifying tragedy" in an interview with a German television station late last month.

He is due to appear in a closed session of parliament on Tuesday in response to a petition signed by 54 lawmakers.

Holocaust denial has been a staple theme of public speeches in Iran since the 1979 Islamic revolution. Former President Mahmoud Ahmadinejad took this further by calling Nazi crimes against Jews "a myth."

Ahmadinejad's views hurt Iran's international image and helped to energize international efforts to curb its nuclear program, which the West suspects is aimed at obtaining a nuclear weapon but which Tehran says is entirely peaceful.

New reformist President Hassan Rouhani has tried to undo the damage by adopting a more conciliatory tone and engaging in negotiations with world powers to settle the nuclear dispute.

In sharp break with his predecessor, Rouhani himself called the Holocaust "reprehensible" in a U.S. television interview.

(Reporting by Mehrdad Balali; Editing by Alistair Lyon)