Iranian President Mahmoud Ahmadinejad attacked Western powers on Thursday for a catalogue of misdeeds, but his address to the United Nations failed to mention Tehran's disputed nuclear program.

The U.S. delegation walked out when Ahmadinejad said "arrogant powers" threatened anyone who questioned the Holocaust and the Sept. 11 attacks on the United States with sanctions and military action. Other Western delegations soon made their exit.

Ahmadinejad made only a passing reference to the Palestinian issue which has overshadowed this year's UN General Assembly and did not comment on the Palestinian plan to ask the UN Security Council to recognize their nascent state.

He accused the United States of using the "mysterious" Sept. 11, 2001, attacks as a pretext to launch wars on Iraq and Afghanistan. The United States and its allies "view Zionism as a sacred notion and ideology," the Iranian leader said.

"By using their imperialistic media network which is under the influence of colonialism they threaten anyone who questions the Holocaust and the Sept. 11 event with sanctions and military actions," he added.

Mark Kornblau, spokesman for the U.S. mission at the United Nations, condemned Ahmadinejad's remarks." "Mr Ahmadinejad had a chance to address his own people's aspirations for freedom and dignity, but instead he again turned to abhorrent anti-Semitic slurs and despicable conspiracy theories," Kornblau said in a statement.

Ahmadinejad's address also passed in silence over the pro-democracy uprisings that have swept the Arab world this year, including Syria, Iran's closest Arab ally.

U.S. President Barack Obama told the United Nations on Wednesday that Iran and North Korea risked more pressure if they pursued nuclear programs that flouted international law.

"There is a future of greater opportunity for the people of these nations if their governments meet their obligations. But if they continue down a path that is outside international law, they must be met with greater pressure and isolation," he said.