The hardliner also vowed that Iran will not back down "one iota" in the face of international pressures over the atomic work, which the West fears may be a cover for weapons development despite Iran's persistent denial.
"They issued several resolutions and sanctioned Iran … They think Iranians will fall on their knees over these things but they are mistaken," Ahmadinejad said in a speech in southern Iran carried live on state television.
"We are not interested in conflicts (but) you are continually demanding things," he said to world powers, led by the United States, which are seeking to curb Iran's atomic ambitions.
"They should not think they can put up obstacles in Iranians' way … I assure the people … that the government will whole-heartedly defend Iran's rights and will not back down one iota," he said.
Iran is already under three sets of UN Security Council sanctions over its defiance and refusal to suspend enrichment, which lies at the heart of international fears about its nuclear programme.
The process that makes nuclear fuel can also be used to make the fissile core of an atomic bomb.
World powers gave Iran until the end of 2009 to accept a UN-brokered deal to ship most of Iran's low-enriched uranium (LEU) abroad to be further refined into reactor fuel by Russia and France.
But the deadline was ignored, prompting talk of fresh sanctions against the Islamic republic.
Iran has in return insisted on its counter-proposal of a staged swap of LEU for nuclear reactor fuel.
Some Western powers have dismissed Iran's proposal and asked Tehran to accept an offer made by the UN nuclear watchdog, the International Atomic Energy Agency, which surfaced during talks in October between Iran and permanent Security Council members plus Germany.
But Iran's Foreign Minister Manouchehr Mottaki said that Tehran was still awaiting a response from world powers on its proposal.
"We have sent them a message which was well received," Mottaki was quoted a saying by Fars news agency on Saturday.
"We are waiting to receive a practical response… and then we will announce our views," he said.
The Iranian leadership has also drawn international condemnation over its treatment of anti-government protests triggered by Ahmadinejad's June 12 disputed re-election.
On Saturday Ahmadinejad dismissed criticism of Iran over human rights as a "game."
"They cannot break the people and the Islamic republic by such pressure and propaganda," he said after inaugurating a new aluminium plant in the southern port city of Bandar Abbas.
The US administration is reportedly crafting new financial sanctions targeting the Iranian entities and individuals most directly involved in the crackdown on anti-government protesters.
Citing unnamed US officials, the Wall Street Journal said on Saturday that US Treasury Department strategists had already been focusing on Iran's Revolutionary Guard Corps, which has emerged as the economic and military power behind supreme leader Ayatollah Ali Khamenei and Ahmadinejad.
