Annan said freedom of expression has to be exercised with "respect, sensitivity, and judgment."
At a news conference in Tehran following talks with Iranian President Mahmud Ahmadinejad, Annan said: "I think the tragedy of the Holocaust is a sad and undeniable historical fact. So we should really handle that, accept that fact, and teach children in World War II to ensure that it is never repeated."
Ahmadinejad has called the killing of 6 million Jews in Nazi-occupied Europe during World War II a myth.
Earlier today an Iranian foreign ministry spokesman said Iran will go ahead and sponsor a conference to examine the scientific evidence supporting the Holocaust.
Hamid Reza Assefi said both opponents and proponents of the existence of the Holocaust could participate.
Assefi did not disclose where and when the Holocaust conference would be held. Iran first raised the possibility of the conference in January.
President Ahmadinejad visiting the tomb of Ayatollah Ruhollah Khomeini in October (Fars)
READEach year in Iran, the last Friday of Ramadan is celebrated as Qods (Jerusalem) Day, officially a day for expressing solidarity with the Palestinian people.
"I have been notifying the Muslims of the danger posed by the usurper Israel," Ayatollah Ruhollah Khomeini, father of Iran's Islamic Revolution, said in an August 1979 announcement. "I ask all the Muslims of the world and the Muslim governments to join together to sever the hand of this usurper and its supporters...and, through a ceremony demonstrating the solidarity of Muslims worldwide, announce their support for the legitimate rights of the Muslim people..." (more)
INTERVIEW: On December 22, 2005, RFE/RL's Radio Farda spoke with FRED ZEIDMAN, director of the U.S. Holocaust Memorial Museum in Washington, D.C. Zeidman commented on Iranian President Mahmud Ahmadinejad's anti-Israeli comments.
ARCHIVE: For an archive of RFE/RL's coverage of Iran, click here.