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” that it halt uranium enrichment.

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 (IAEA), which is the U.N. nuclear watchdog agency.

When Ahmadinejad was ushered to the podium of the General Assembly to speak, 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 hours after French President Nicolas Sarkozy warned the assembly that allowing Iran to arm itself with nuclear weapons would be an “unacceptable risk to stability in the region and in the world.”

Earlier, German Chancellor Angela Merkel threatened tougher sanctions against Iran if the country remained intractable on the dispute over its nuclear program.

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.

Ahmadinejad has defied two Security Council resolutions demanding Iran suspend enrichment and imposing escalating sanctions on key figures and organizations involved in the nuclear program. He made clear in his speech that Iran did not intend to comply with them now.

“In the last two years, abusing the Security Council, the arrogant powers have repeatedly accused Iran and even made military threats and imposed illegal sanctions against it,” he said.

“Fortunately, the IAEA has recently tried to regain its legal role as support of the rights of its members while supervising nuclear activities,” he added. “We see this as a correct approach adopted by the agency.”

As a result, Ahmadinejad said, “I officially announce that in our opinion the nuclear issue of Iran is now closed and has turned into an ordinary agency matter.”

Earlier this month, IAEA chief Mohamed El-Baradei said Iran’s cooperation with the agency represented an important step, but he urged Tehran to answer all questions – including reported experiments that link enrichment and missile technology – before the end of the year.

This week, IAEA technical officials returned to Tehran to deal with the nuclear questions. But while Iran is allowing the IAEA to inspect its known nuclear facilities, it no longer allows inspectors freedom to look elsewhere for suspicious activities on short notice as it once did.

El-Baradei recently proposed a compromise under which Iran would agree to answer questions on past nuclear activities, some of them with possible weapons applications, that it had refused to answer in the past. Tehran pledged to respond by the end of the year.

The U.S. initially opposed the plan, fearing it could draw attention away from Iran’s defiance of the Security Council demand for a halt to Iranian uranium enrichment. It later endorsed the plan while emphasizing that Iran must obey the council.

Speaking to reporters after his speech, Ahmadinejad sought to clarify Tehran’s stance on the nuclear standoff, which he blamed on “certain big powers” that have sought “to turn a simple legal issue into a very loud, controversial political issue.”

He said Tehran’s stance is that the matter involves only legal issues for the IAEA to handle, alluding to the Iranian regime’s insistence that it is following its commitments under the Nuclear Nonproliferation Treaty to use nuclear power only for peaceful purposes.

In his speech to the assembly, Sarkozy called for the international community to be firm in pressuring Iran.

“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.”

Sarkozy’s comments came after Germany’s leader threatened tougher sanctions against Iran if the country remains intractable. Merkel said an Iranian nuclear bomb would have devastating consequences not only for Israel and the whole of the Middle East, but for Europe and the rest of the world.

“For this reason, the international community must not let itself become splintered” in dealing with Iran, Merkel told reporters in New York. “The world should not have to prove to Iran that it is building a bomb, but Iran must convince the world that it doesn’t want to build a nuclear bomb.”

Iran was not without allies. Nicaragua’s leftist President Daniel Ortega angrily chastised the U.S. for seeking to stop other countries from enriching uranium, which is allowed under the Nonproliferation Treaty.

Ortega said the United States, as “the only country in the world to have dropped nuclear bombs on innocent people,” had no right to question the right of Iran and North Korea to pursue nuclear technology for “peaceful purposes.”

“And even if they want nuclear power for purposes that are not peaceful, with what right does (the U.S.) question it?” he told the world leaders.

Ortega has promised to maintain ties with Washington since taking office again in January, but also has signed a series of accords with Iran.

Earlier in the assembly’s opening session, U.N. Secretary-General Ban Ki-moon pledged to push for lasting peace in the Middle East.

Associated Press writers George Jahn in Vienna, Austria, and Sarah DiLorenzo in New York contributed to this report.