The president said on Monday Western powers "know that any change in Palestine will change the world's political, economic and cultural arrangement, and therefore they support the Zionist regime's most wicked deeds".
"The world is on the verge of change, and more than before we can hear the sound of this present, unstable order breaking down," the student news agency ISNA quoted him as telling a conference entitled Supporting the Islamic Revolution of Palestine.
"If the massacre of the Jews in Europe is true and used as an excuse to support Zionists, why should the Palestinians pay the price?" he added, repeating a comment that has widely been interpreted as support for deniers of the Holocaust.
Ahmadinejad, who in October said arch-enemy Israel should be "wiped off the map", said last week that if Germany and Austria believed Jews were massacred during the second world war, a state of Israel should be established on their soil.
His comments again drew widespread international condemnation, and the UN Security Council also issued a statement to "condemn the remarks about Israel and the denial of the Holocaust attributed to Dr Mahmoud Ahmadinejad".
"If the massacre of the Jews in Europe is true and used as an excuse to support Zionists, why should the Palestinians pay the price?"
But Ahmadinejad said: "Western policy in regards to Palestine has always been in favour of the Zionist regime and harmed the Islamic world, and they cannot be the mediators and judges on the issue.
"All Islamic countries must strive to change the Islamic world's stance after 60 or 70 years in a passive state," he said.
Elected on a platform of restoring the purity of the Islamic revolution, Ahmadinejad's stance has already worried European countries seeking to strike a deal over Tehran's controversial nuclear programme.
Despite its fiery rhetoric, the Iranian government says its nuclear programme is merely designed to meet domestic energy needs.