Ahmadinejad already called the Nazis' World War II slaughter of European Jews a "myth" and said the Jewish state should be wiped off the map or moved to Germany or the United States.
Those remarks prompted a global outpouring of condemnation, and it wasn't clear who would be willing to attend an Iranian-sponsored Holocaust conference.
Late last year, however, the leader of Egypt's main Islamic opposition group joined Ahmadinejad in characterizing the Holocaust as a "myth" and lambasted Western governments for criticizing those who dispute the Jewish genocide happened.
"Western democracies have slammed all those who don't see eye to eye with the Zionists regarding the myth of the Holocaust," Muslim Brotherhood chief Mohammed Mahdi Akef wrote on the group's Web site.
Tehran already had further raised international concern about its nuclear program last week when it resumed what it called "research" at its uranium enrichment facility.
The International Atomic Energy Agency, the U.N. organization that monitors nuclear proliferation, said Iran was resuming small-scale nuclear enrichment, a process that can produce fuel for atomic bombs.
That, in turn, prompted Washington and its allies to renew their push to take Iran before the U.N. Security Council for the possible sanctions.
The United States, its European allies and Japan believe Tehran is trying to build a nuclear weapon. Iran denies the charge and says its nuclear program is only for electricity generation.
In calling for penalties against Iran's "irresponsible" behavior, Republican Sen. Trent Lott pointed to Tehran's plans for the Holocaust conference.
"At the minimum, we should go to the U.N. Security Council and we should impose economic sanctions unless there is some dramatic change in the Iranian position," he said on CNN's "Late Edition."
Rep. Tom Lantos, D-Calif., a Holocaust survivor who was born in Budapest, Hungary, also has said he understood Iran was considering a conference that would call into question evidence that the Nazis conducted a mass murder of European Jews during World War II.
Foreign Ministry spokesman Hamid Reza Asefi did not disclose where or when the Holocaust conference would be held, nor would he say who would attend or what had prompted Tehran to sponsor it.
On Saturday, however, Ahmadinejad urged the West to be sufficiently open-minded to allow a free international debate on the Holocaust. Asefi adopted that theme.
"It is a strange world. It is possible to discuss everything except the Holocaust. The Foreign Ministry plans to hold a conference on the scientific aspect of the issue to discuss and review its repercussions," Asefi told reporters.
Earlier this month, the Association of Muslim Journalists, a hard-line group, proposed holding a similar conference, but Asefi said he was not aware of the association's wishes. He said the conference he announced was planned and supported by the ministry.
Israel and Iran had good relations until the 1979 Islamic revolution, lead by Grand Ayatollah Ruhollah Khomeini, deposed Shah Mohammad Reza Pahlavi. Israel had backed the shah, apparently prompting Khomeini to term it the "Little Satan."
Ahmadinejad has adopted rhetoric reminiscent of Khomeini, seemingly trying to breath life back into the waning revolutionary spirit in the country, whose residents are not traditionally anti-Jewish.
Before the revolution about 100,000 Jews lived in Iran, but three-fourths fled during the upheaval.
Ahmadinejad, who took office in August, caused an international outcry in October by calling Israel a "disgraceful blot" that should be "wiped off the map."
Leaders around the world also condemned him after he called the Nazi slaughter of Jews during World War II a "myth." He later said that if the Holocaust did happen, then Israel should be moved to Germany or North America, rather than making Palestinians suffer by losing their land to atone for crimes committed by Europeans.
Since the Islamic revolution, Israel has considered Iran a primary and existential threat. As Tehran's nuclear program has moved forward, the Israelis - who have nuclear weapons but do not to admit possessing such an arsenal - have refused to rule out using military force to destroy the Iranian program.