Iran has escalated its war of words with the US over Tehran's nuclear programme, calling Washington's arsenal a major threat to global peace.
Kharrazi was uncompromising in his speech at the UN
Iranian Foreign Minister Kamal Kharrazi demanded assurances that the US would not launch a nuclear strike on Iran.
And he rejected a call from President George Bush for non-nuclear nations to be denied access to nuclear technology.
The US fears Iran is trying to build nuclear arms. Iran says its nuclear programme is for civilian use only.
Mr Kharrazi told a UN conference it was unacceptable for an "exclusive club" of nations to deny nuclear technology to others "under the pretext of non-proliferation".
Iran has indicated it will soon resume some nuclear activities, but will stop short of full-blown uranium enrichment.
Foreign ministry spokesman Reza Asefi said Iran would maintain its freeze on enrichment - suspended since November - as long as talks on its nuclear programme continued with Germany, France and the UK.
German Foreign Minister Joschka Fischer earlier warned that any resumption of nuclear activities would spell the end of negotiations, in which the Europeans hope to persuade Iran to give up its nuclear research.
He said restarting the programme could lead to referral to the UN Security Council - something for which the US has long lobbied.
But Mr Kharrazi told the conference in New York that Iran was determined to resume uranium enrichment at some stage.
"Iran for its part is determined to pursue all legal areas of nuclear technology including enrichment exclusively for peaceful purposes," he said.
GLOBAL NUCLEAR POWERS
Signed the NPT: US, Russia, UK, France, China
Declared or known: India, Pakistan, Israel
Suspicions over: North Korea, Iran
Formerly had programmes: Algeria, Argentina, Belarus, Brazil, Kazakhstan, Iraq, Libya, Romania, South Africa, Ukraine
Iran has long insisted that its suspension of uranium enrichment is voluntary and temporary.
The UN is holding a month-long conference reviewing the 1970 nuclear Non-Proliferation Treaty (NPT), which is aimed at reducing the threat from nuclear arms.
Three senior Iranian officials have now said that some enrichment activities will begin soon at the uranium conversion plant outside the city of Isfahan.
They have said it is unlikely they will resume actual enrichment - injecting uranium gas into centrifuges - but the BBC's Frances Harrison in Tehran says this distinction will be lost on the rest of the world.
Our correspondent says it is not clear whether this is just brinkmanship from Iran to try to secure more concessions from Europe, or a serious threat aimed at ending the nuclear negotiations.
The NPT is reviewed every five years, with delegates from all 187 signatory states participating in the conference.
ESTIMATED NUCLEAR WARHEADS, STRATEGIC AND TACTICAL
*The US is also said to have some 3,000 warheads in reserve, while Russia has about 11,000 in non-operational stockpiles
Israel declines to confirm it has nuclear weapons
North Korea claims it has nuclear arms but no details are available
Iran is accused by the US of ambitions to build nuclear arms