"The roots of the main problems in the world today should be sought in the behavior of the U.S. administration," Mahmoud Ahmadinejad said during a meeting with UN Secretary General Ban Ki-moon in New York.
The Iranian leader also reiterated that the Islamic Republic's nuclear program was entirely peaceful and dismissed U.S. accusations that Tehran was striving to develop nuclear weapons.
He also said Iran was determined to resolve its nuclear problem by peaceful means, but would require "a just approach" from the West.
In an interview with National Public Radio, Ahmadinejad said that, "We do not have confrontations with anyone. The U.S. administration interferes, and we defend ourselves."
Speaking to the Los Angeles Times, he said that the current global financial crisis had been caused by U.S. military interventions around the world.
"Problems do not arise suddenly," he said. "The U.S. government has made a series of mistakes in the past few decades. The imposition on the U.S. economy of years of heavy military engagement and involvement around the world . . . the war in Iraq, for example. These are heavy costs imposed on the U.S. economy."
Several hundred people rallied outside the UN headquarters in New York to protest Ahmadinejad's arrival for the General Assembly session.
The Iranian president is due to speak at a UN session on Tuesday - a day after the IAEA said it had not been able to make much progress in its inquiry into a possible military aspect to Iran's nuclear program. The UN nuclear watchdog added that the issue remained a serious concern.
Tehran says its nuclear activities are aimed at generating electricity, but the United States and other Western nations suspect the civilian program is a cover for plans to build a nuclear bomb. The United States and Israel have refused to rule out a military attack on the country's nuclear facilities.
Foreign ministers from the six powers engaged in the long-running nuclear talks with Iran - Russia, China, the U.S., France, Britain, and Germany - will meet on Thursday on the sidelines of the UN General Assembly, the French Foreign Ministry said earlier.
Russia and China, veto-wielding UN Security Council members, have opposed extra, tougher sanctions against Tehran over its defiance of international demands to halt uranium enrichment, a process needed in power generation and weapons production.
Russia has urged Iran to comply with all UN Security Council resolutions and UN nuclear watchdog rulings on its nuclear program.
