He also suggested that "Zionists and Jews" were culpable for killing black babies and starting the Russian Revolution nearly a century ago.
Abraham Foxman, the ADL's national director, called for UN Secretary General Ban Ki-moon "to speak out and to make clear that these views are not only objectionable, but repugnant to the entire international community".
He said Mr Rahimi's claims of a Zionist conspiracy made it clear that antisemitism is still alive and well. "What makes it more sinister and dangerous is the fact that it comes from a leader of a country that has vowed to destroy the Jewish state, and is making efforts to obtain the means to do it," he said.
"One would hope that this resurgence of dangerous antisemitic themes at a UN conference in Tehran would shake up the moral, political, religious leadership to condemn it with a strong voice."