Tehran's hardened stance came on the eve of its self-imposed deadline to formally respond to a six-nation package which includes both incentives aimed at persuading Iran to suspend uranium enrichment and possible sanctions if Iran does not comply.

"The Islamic Republic of Iran has decided to continue its path powerfully regarding the nuclear energy issue," the state television quoted Supreme Leader Ayatollah Ali Khamenei as saying on Monday.

"Bullying powers and the United States have imposed huge pressure on Iran while they know that Iran is not developing nuclear weapons," he added.

The United States has accused Iran of secretly developing nuclear weapons under a civilian front, a charge categorically denied by Tehran which says that its nuclear program is for peaceful purposes.

The Iranian leader did not directly mention the nuclear proposal agreed on in June by the five permanent members of the UN Security Council -- the United States, Russia, China, France and Britain, -- plus Germany. Iran has promised to give an official response by Aug. 22.

In another sign of Iran's defiant stance, Deputy Director of Iran's Atomic Energy Organization (AEO) Mohammad Sa'eedi said Monday that suspension of uranium enrichment was "practically impossible" even though the UN Security Council had made such a demand.

"Considering the technical progresses made by the Iranian scientists in the nuclear ground, suspension of uranium enrichment has now turned practically impossible," local Fars news agency quoted Sa'eedi as saying.

The UN Security Council adopted a resolution last month urging Tehran to suspend by Aug. 31 all enrichment-related and reprocessing activities, including research and development, or face the prospect of sanctions.

Iranian officials have rejected the resolution as having no legality and vowed to retaliate if sanctions are imposed on it.

The chairman of the Iranian parliament's National Security and Foreign Policy Commission, Alaeddin Boroujerdi, warned Monday that Iran might kick out International Atomic Energy Agency (IAEA)inspectors if it faces sanctions.

"We have a plan at the commission which rules for the halt of IAEA inspections in case rights of the Iranian nation are ignored and sanctions are imposed on us," Fars news agency quoted Boroujerdi as saying.

"In compliance with the same bill, we are studying the possibility of removing IAEA cameras now installed in our nuclear power plants," he told reporters on the sidelines of an open session of the parliament.

Meanwhile, Iranian officials confirmed that Tehran had finished considering the six-nation offer aimed at settling the nuclear dispute and would present its response on Tuesday. Sa'eedi, the Iranian nuclear official, said Tehran's answer would be "very comprehensive and provide a very convenient opportunity for the West to move towards solving the case through negotiations."

Iran would not propose any parallel or counter plan to replace the six-nation package, he added.

Meanwhile, Iran's giant heavy-water project will become operational in the near future, Sa'eedi said, adding that the achievement will make Iran the ninth country to own a heavy-water production complex in the world.

The IAEA has asked Iran to reconsider its plans to work on the heavy water research reactor at Arak, 230 km south of Tehran.

Heavy water reactor could produce plutonium, a material that can be used in making nuclear bombs.

Iranian Foreign Minister Manouchehr Mottaki, who is on a visit to South Africa, said on Monday that he hoped a comprehensive agreement could be reached.

"We hope there is some cooperation and negotiation respecting the right of Iran to have nuclear technology and remove any questions," Mottaki said in Pretoria, South Africa's capital.