Appearing on state television, Ahmadinejad said any further UN resolutions would not prevent Iran from obtaining nuclear technology.
"Let's say [the Security Council] issued Resolution Number 300, Resolution 299, and so on -- what will happen then? We should remember that Iran is becoming a nuclear state," Ahmadinejad said.
Two sets of UN sanctions have been imposed on Iran for defying Security Council resolutions demanding it suspend all nuclear fuel-production activity.
The so-called 5+1 group -- of permanent Security Council members (China, France, Russia, United States, and United Kingdom) plus Germany -- has led the UN effort at curbing Tehran's nuclear ambitions.
U.S. officials have accused Iran of secretly trying to develop nuclear weapons. Officials in Iran have repeatedly denied any such intention.
Ahmadinejad attacked the countries that have backed the sanctions. You have committed an illegal act [with UN sanctions], so you must terminate it and begin talks," he said. "There is no sense in any of this. You are being unjust. If we suspend our work, there is nothing left to talk about."
Iran says that as a member of the Nuclear Nonproliferation Treaty (NPT), it has the right to enrich uranium. On July 25, the British daily "The Independent" quoted Iran's top nuclear negotiator, Ali Larijani, as saying that uranium enrichment is "like breathing" for his country.
Two days before that, British Prime Minister Gordon Brown warned that a third UN resolution might follow if Iran does not suspend all its nuclear-fuel-production activities.
"We are going to have to consider what we do in future -- there will probably be a third [Security Council] resolution in relation to Iran soon, and I believe that that is a way forward that is working and will work," Brown said. "And again, I appeal to the Iranian authorities to understand the fears that other countries have about the development of a nuclear weapons program."
Iran insists its nuclear program is entirely peaceful. But the international community remains suspicious and the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), unconvinced.
Ahmadinejad on July 25 described Iran's nuclear activities once again as "peaceful" and "legal." He said Tehran sees no reason why it should halt any nuclear activities, and he rejected any preconditions that would include stopping uranium enrichment.
Apparently addressing the Security Council, Ahmadinejad accused the UN of "illegally" imposing sanctions:
"You [the Security Council] have committed an illegal act, so you must terminate it and begin talks," Ahmadinejad said. "There is no sense in any of this. You are being unjust. If we suspend our work, there is nothing left to talk about."
While Iranian officials have remained firm in public pronouncements, they have been negotiating with the IAEA over its demand that Tehran clarify the scope of its nuclear work.
On July 24, Iran agreed with the IAEA to allow UN inspectors revisit a heavy-water reactor facility at Arak early next week.
That visit comes four months after Iran cut off inspectors' access to the site to protest the UN sanctions.
According to Iran's semi-official Fars news agency, the IAEA inspectors were due to arrive in Tehran today.
Some observers regard Iran's renewed cooperation with the IAEA as an attempt to avoid any escalation of the nuclear crisis ahead of a UN Security Council meeting in September.
"The Guardian" newspaper reported on July 25 that -- in response to Iran's fresh overtures to the IAEA -- debate among global powerhouses on a new round of sanctions have been "quietly shelved" until August.
THE COMPLETE PICTURE: RFE/RL's complete coverage of controversy surrounding Iran's nuclear program.
An annotated timeline
of Iran's nuclear program.