"At the beginning of the (1979 Islamic) revolution, we stood up to identical pressure and we are used to it. The Islamic republic has no intention of giving in to pressure," powerful former president Akbar Hashemi Rafsandjani was quoted as saying in his latest comment on the deadline.
On Friday, the International Atomic Energy Agency (IAEA) gave Iran until October 31 to clear up widespread suspicions it is using an atomic energy programme as a cover for nuclear weapons development.
The resolution, passed by the IAEA's board of governors after intensive US lobbying, demands Iran answer all the IAEA's questions regarding its enrichment activities, provide unrestricted access to IAEA inspectors and provide a detailed list of its nuclear-related imports.
One of the IAEA's demands is that Iran sign an additional protocol to the nuclear Non-Proliferation Treaty, which would allow inspectors to make surprise visits to suspect sites.
Failure to satisfy the IAEA could see Iran declared in violation of the NPT on November 20, when the board convenes again in Vienna. The issue could be referred to the UN Security Council, leading to the possible imposition of sanctions.
Even some key reformists have rejected the ultimatum.
Parliamenetary speaker Mehdi Karrubi, a close ally of President Mohammad Khatami, said the IAEA resolution was "political".
"The Iranian people will not accept giving in to the logic of force," he was quoted as saying by the official news agency IRNA.
And a prominent conservative, justice chief Ayatollah Mahmoud Hashemi Shahrudi, qualified the resolution as "unjust".
"The US and their allies want to stop Iran from accessing new technology," he was quoted as saying on state radio. He said the "only solution was to resist".
Embattled President Khatami, however, on Wednesday maintained his silence on the crisis when asked for his reaction to the resolution.
Iran's official position on the resolution has been spelled out by the foreign ministry, which stated that "the nature of our cooperation with the IAEA is under consideration."