Ayatollah Ali Khamenei told a gathering of Iranian ambassadors late Monday that "the position of the United States and certain Western countries, which require Iran to give up nuclear technology is unsuitable, unjust and oppressive, and the Islamic Republic of Iran will never accept these requests."
"The conditions in which the United States deals with the rest of the world as a creditor, always asking for more, make any weakness and surrender the greatest strategic error," the state news agency IRNA reported him as saying.
"Iranian nuclear science is indigenous and peaceful, and the Islamic Republic of Iran, based on religious principles, will never use weapons of mass destruction," Khamenei added.
On Monday Tehran said it was still discussing with the International Atomic Energy Agency (IAEA) whether to allow snap UN inspections of its nuclear sites.
"We are still discussing the additional protocol" to the nuclear Non-Proliferation Treaty (NPT), foreign ministry spokesman Hamid-Reza Asefi said.
Tehran is under strong international pressure to prove it is not secretly developing atomic weapons by signing the extra NPT clause, which would allow UN inspectors to descend on suspect sites without warning.
The IAEA's board of governors will review the Iranian case on September 8, with the threat that it might be forwarded to the UN Security Council.
Asefi told reporters "to wait and see what will happen during the (September 8) meeting."
"Any decision will depend on the explanations given by the agency, on the ambiguities that exist (over the additional protocol), our responsibilities and those of the international community with regard to Iran," he added.
Oil-rich Iran said Thursday it was going ahead with the second phase of a nuclear power plant to satisfy its growing demand for power and prevent long-term energy shortages, denying US allegations that it is covertly developing nuclear weapons.