“Iran will announce in the next few days some very important and major nuclear achievements,” Ahmadinejad said at a rally attended by tens of thousands of people to mark the 33rd anniversary of the 1979 Islamic revolution.

Ahmadinejad’s appearance at the Freedom Square rally was met by sustained cheers from demonstrators holding portraits of Iran’s supreme leader, Ayatollah Ali Khamenei, and placards that read “Down With USA” and “Down With Israel.”

The rally, which took place at the foot of the snowy Alborz mountains, was also attended by Ismail Haniya, the head of the Islamist group Hamas in the Gaza strip. A military helicopter swooped low over the crowd to scatter confetti after Ahmadinejad’s arrival.

Ahmadinejad was speaking amid increasing tensions over Iran’s nuclear program, which Western countries and Israel suspect is aimed at the creation of atomic weapons. Iran says the program is designed solely for the production of civilian energy.

The United States and European countries have recently tightened sanctions against Iran and the European Union will ban Iranian oil imports by July.

Speculation has also been growing in recent weeks that Israel may launch an attack against Iran to counter what it describes as a major threat to its national security.

The United States has also refused to rule out force. The U.S. Defense Secretary Leon Panetta was reported as saying earlier this month there was a strong possibility Israel could strike between April and June this year.

Iran has warned it will respond militarily to any attack. It has also threatened to block the Strait of Hormuz, a vital Gulf shipping route. Iranian Foreign Minister Ali Akbar Salehi told state television on Friday that Iran was “prepared” for the “worst case” scenario.

“The Islamic Republic of Iran takes these threats seriously and we are prepared in every respect and have plans for the worst-case scenarios,” Salehi said, as reported by Iran’s English-language Press TV website.

Ahmadinejad was defiant on Saturday, warning the West that it would never force Iran to succumb to pressure.

“Study our history, our culture,” he said. “I tell you openly, the Iranian nation will never give in to the language of force.

“The West and Israel think only of their own interests… but they must know their time will come,” he said.

Members of Iran’s elite Revolutionary Guard pumped their fists in the air after Ahmadinejad’s comments.

Ahmadinejad also reiterated that Tehran was open to a revival of international talks on its nuclear program, but said that the West must “respect Iran’s rights.”

“We have always been prepared to hold talks in a framework of equality ad mutual respect,” he added.

Peaceful Nuclear Energy or Nuclear Weapons?

Iran says it has an inalienable right to nuclear energy and has refused to discuss uranium enrichment. Western powers say there is no point to talks without a discussion of the issue.

Sanctions are already biting in Iran, with prices for basic food stuffs having doubled in recent weeks. But shopkeepers were unwilling to go on record about inflation.

“I don’t need any problems,” one store owner said. “Our government has not mentioned the price increases and I might say the wrong thing.”

Commodities traders said this week that Iran was engaging in barter trade, using gold or oil for food, to get around payments problems in international banks closed by sanctions.

The demonstrators at Saturday’s rally, many of whom had been bussed in for the event, appeared ready to make sacrifices for the sake of Iran’s nuclear rights.

“I will become a nuclear scientists,” read a placard worn by one small girl. “No more negotiations!” read another placard held by a teenager.

Ahmadinejad denied on Saturday that sanctions were having a major effect, saying the economy was in good shape.

Revolution Day saw clashes between police and opposition protesters in 2009 but there were no reports of disturbances Saturday. Email services on the eve and day of the rally were down across Tehran.

The rally came just weeks before parliamentary elections, the first major polls in Iran since the disputed 2009 presidential vote at which Ahmadinejad secured a second term.

Opposition figures claim the vote was rigged and eight months of protests ensued before a government crackdown finally put an end to the demonstrations.