Iran has said it is determined to produce nuclear fuel on its own territory in defiance of international calls to halt the work.
It has also accused the United States of trying to prevent a negotiated solution to its dispute with the West.
Iran's chief nuclear negotiator, Ali Larijani, said Iran was still reviewing nuclear proposals backed by six nations and wanted talks to solve the dispute.
But he said the US 'has been trying to create obstacles in the way of talks and a diplomatic solution to this issue'.
Mr Larijani warned that Iran would have to 'review its nuclear policies' if confrontation was chosen instead of talks.
Iranian officials have previously threatened, if pushed, to review cooperation with the UN atomic watchdog, the International Atomic Energy Agency, and the country's adherence to the nuclear Non-Proliferation Treaty.
The five permanent members of the UN Security Council, China, US, Russia, Britain and France, plus Germany, have proposed that Iran halts nuclear enrichment in return for economic and diplomatic incentives.
UNSC members are currently engaged in informal talks in New York on how to make legally binding demands that Iran suspends uranium enrichment and stops work on a reactor that can produce plutonium.
Iran has said it would reply to the package by 22 August, defying international calls for a swifter response.
Iran's nuclear file has now been referred back to the UNSC after Tehran took too long to reply to the offer.
Tehran insists it only wants to master enrichment in order to make fuel for nuclear power plants.
