United Nations ? Iranian leader Mahmoud Ahmadinejad declared Tuesday that Iran’s disputed nuclear program is closed as a political issue and said Tehran will ignore a U.N. Security Council demand imposed by “arrogant powers” to curb its nuclear program.

Instead, he told world leaders at the U.N. General Assembly that Iran has decided to pursue the monitoring of its nuclear program “through its appropriate legal path,” the International Atomic Energy Agency, which is the U.N. nuclear watchdog agency.

When Ahmadinejad was ushered to the podium, the U.S. delegation walked out, leaving only a low-ranking note-taker to listen to his speech, which indirectly accused the United States and Israel of major human rights violations.

The Iranian president spoke shortly before German Chancellor Angela Merkel warned the diplomats of “disastrous consequences” for Israel and the world if Iran acquires a nuclear bomb. “The world does not have to prove to Iran that Iran is building a nuclear bomb. Iran has to convince the world that it is not striving toward such a bomb.”

Hours earlier, French President Nicolas Sarkozy told the assembly that allowing Iran to arm itself with nuclear weapons would be an unacceptable risk. “There will not be peace in the world if the international community falters in the face of the proliferation of nuclear arms,” Sarkozy said. The Iranian crisis “will only be resolved if firmness and dialogue go hand-in-hand.”

Iran insists the program is purely peaceful, aimed solely at using nuclear reactors to generate electricity. But the United States and key European nations believe the program is a cover for an Iranian attempt to produce nuclear weapons.