Iranian Supreme Leader Seyed Ali Ali Khamenei vowed in Tehran on Thursday that Iran is fixed to resist any pressure and conspiracy imposed on the country's nuclear program.

"During the past 27 years, we have experienced such situations for many times. Now, the Iranian nation is determined to resist any pressure or conspiracy," Khamenei was quoted by state television as saying.

"We will forge ahead with the work toward mastery of nuclear technology," Khamenei said.

Earlier in the day, Iranian President Mahmoud Ahmadinejad said Iran would never give in to bullies on its nuclear issue, for nuclear energy is an undeniable right of the country.

"The Iranian nation will never give in to bullies, and all of them are announcing that nuclear energy is an undeniable right," Ahmadinejad was quoted by the official IRNA news agency as saying in the western province of Lorestan.

Ahmadinejad said the time of bullying over the Iranian nuclear issue had come to an end, and Iran would never be forced to do anything.

The hardline comments of the two top Iranian officials came just one day after the country's nuclear file was formally sent to the U.N. Security Council.

On Wednesday, the International Atomic Energy Agency (IAEA) board of governors concluded a key seasonal meeting in Vienna.

Although discrepancies still remained within the IAEA board on its next move on Iran, IAEA chief Mohamed ElBaradei's report on the Iranian nuclear issue was handed over to the U.N. Security Council soon after the meeting.

ElBaradei stressed that the involvement of the Security Council was "just a new phase of diplomacy, not the end of it."

Iran has said it will continue talks with the international community to find a solution to its nuclear dispute despite the negative situation.

Echoing Khamenei and Ahmadinejad, Iran's Majlis (parliament) Speaker Gholam-Ali Haddad-Adel also criticized the western approach on its nuclear issue as "dual attitude", saying opposition to Iran's nuclear pursuit "runs counter to the nuclear Non-Proliferation Treaty (NPT)."

"The United States backs Israel, which has hundreds of nuclear warheads and is clearly a threat to the world, but opposes Iran's peaceful nuclear research," Adel said at a Majlis session on Thursday.

However, Adel showed some degree of restraint as to a motion put forward by some lawmakers to cease all cooperation with the IAEA which Tehran defined as voluntary, saying the issue should be considered after the Majlis was briefed by all related officials on the nuclear program.

Iran's chief nuclear negotiator Ali Larijani warned on Sunday that the Islamic Republic would have to resume large-scale uranium enrichment if hauled to the U.N. Security Council.

The IAEA board of governors in early February adopted a resolution to report Iran's case to the U.N. Security Council but called on the powerful U.N. body to withhold punitive actions until the meeting in March.

The resolution urges Iran to suspend all work related to uranium enrichment and fully cooperate with the U.N. nuclear watchdog.

However, Iran disallowed IAEA's snap inspections and resumed small-scale enrichment work, a retaliative move against the IAEA resolution.