The two-day conference followed closely behind a 47-nation nuclear security conference hosted by President Barack Obama in Washington last week, which excluded Iran and nuclear-armed North Korea. Washington and its allies suspect Iran's nuclear program is geared toward producing weapons, which Tehran denies.
As the conference was ending Sunday, Iran staged an annual military parade where it displayed missiles capable of carrying nuclear warheads.
The forum, which Iran said was attended by representatives of 60 countries, gave Tehran a platform for challenging Washington's assertion that it wants to see a world without nuclear weapons and for defending its own nuclear program. It criticized what it called a double-standard by some nuclear powers that urge disarmament while ignoring the nuclear arsenal Israel is widely believed to possess.
A nuclear weapons-free Middle East requires "the Zionist regime to join the NPT," said the concluding statement of the conference read out by Iranian Foreign Minister Manouchehr Mottaki.
Israel, which does not confirm or deny possessing nuclear arms, has refused to sign the NPT, which would require it to open up its nuclear facilities to international inspectors.
The conference's statement, also took issue with perceived threats by the US and Israel to attack Iranian nuclear facilities.
"The conference expressed its concerns about the continued existence of Weapons of Mass Destruction - nuclear arms in particular - as well as their application or threat to apply them," the statement said.
Tehran was angered by Obama's announcement this month of a new US nuclear policy in which he pledged America would not use atomic weapons against nations that do not have them. Iran and North Korea were pointedly excluded from the non-use pledge, and Iranian leaders took that as an implicit threat.
'No enemy will dare attack Iran'
Iran's supreme leader, Ayatollah Ali Khamenei, told the conference's opening session on Saturday that the United States' atomic weapons are a tool of terror and intimidation.
Iran also used the weekend gathering to assert its frustration with international pressure to give up the central part of its own nuclear program, which Tehran says is of a peaceful nature and within its rights as a signatory to the NPT.
Israel, the United States and other nations believe Tehran is intent on developing an atomic weapons capability and want it to scrap an accelerating uranium enrichment program that could give Iran a weapons option. Iran denies such an aim and says it only wants to generate power and pursue other peaceful uses for the technology.
Iranian media said China, Russia, Pakistan, Iraq, Turkey and France, as well as delegates from international bodies and non-governmental organizations attended.
Also Sunday, President Mahmoud Ahmadinejad presided over an annual army parade in the capital to demonstrate the fruits of a military industry that he said could deter any attack.
"Today, our armed forces have so much power that no enemy will harbor evil thoughts about laying its hands on Iranian territory," Ahmadinejad said.
The US has been pressing for a new round of international sanctions against Iran after Tehran spurned Obama's offer for dialogue over its accelerated nuclear development.
But, according to a report by The New York Times on Sunday, a January memo from US Defense Secretary Robert Gates to the White House warned that the US lacks a nimble long-term plan for dealing with Iran's nuclear program.
Gates' three-page memo set off efforts in the Pentagon, White House and intelligence agencies to come up with new options, including the use of the military, the Times said, quoting unnamed government officials.
However, White House officials Saturday night strongly disagreed the memo caused a reconsideration of the US approach to Iran.
"It is absolutely false that any memo touched off a reassessment of our options," National Security Council spokesman Benjamin Rhodes told The Associated Press. "This administration has been planning for all contingencies regarding Iran for many months."