Tens of thousands of demonstrators continue to fill the streets of Tehran, protesting the official results of last week's presidential elections and mourning those who have died in the subsequent violence.  Middle East analysts say the dramatic events in Iran are likely to bring fundamental changes to the Islamic Republic.

Before the votes could be credibly counted, according to most analysts, the Iranian government announced the landslide victory of incumbent President Mahmoud Ahmadinejad in the June 12 election.

Soon after, huge crowds supporting opposition candidate Mir Hossein Mousavi poured into the streets of Tehran and other cities to protest the results and express grief for those killed by pro-government militia in post-election violence. Mr. Mousavi is calling for new elections.  

Mohsen Sazegara was a founder of the Iranian Revolutionary Guard Corps and served in several official positions, including Deputy Prime Minister for Political Affairs. He says he became disillusioned with the revolutionary government. He is now an Iranian dissident and political activist.

Sazegara predicts there will be a violent crackdown on anti-government demonstrators.

"What we expect for the people of Iran is supporting democracy, human rights, freedom of speech, freedom of election in Iran," he said. "And people are going to be killed in the streets defending the rights of the people to have their own will to choose their government."

The main power in Iran is held by the Supreme Leader, Ayatollah Ali Khamenei, who most analysts say is a cautious man. For two decades, he has ruled the Islamic republic by controlling the military, the judiciary and government media.

Mehdi Khalaji was trained in Iran as a Shi'ite Muslim theologian and is currently working on a biography of Khamenei. He says he expects the supreme leader, who is a student of the revolution that swept Shah Mohammed Reza Pahlevi from power, to eventually use overwhelming force to crush the opposition.

Khalaji says such a move could put the government into the hands of the military.

"The nature of regime change from a civil government to a military government, if this regime succeeds to crackdown on people, demonstrators on the street, it will lead to some sort of revolution if the government fails to control the situation in the coming days," he said.

Iran has accused the United States of interfering in its electoral process, an allegation Washington denies.

But Patrick Clawson, Director of the Iran Security Initiative at the Washington Institute for Near East Policy, says Khamenei is convinced that Western nations would like to see him swept from power.

"What this means is that Khamenei is going to be formally convinced that we are out to overthrow him, we are behind these very challenging developments," said Clawson. "He is going to read the universal calls by Western governments and Western media to respect the rights of these protesters as proof that there is a mortal threat from the West to his regime and that if he compromises that will only feed this green revolution."

Soon after the election results were announced, Ayatollah Khamenei endorsed President Ahmadinejad's reelection. But as angry crowds swelled in the streets, he backpedaled, saying the Guardian Council, which vets elections and new laws, would investigate the vote and possibly conduct a partial recount.

Michael Singh, a former Senior Director for Middle East Affairs on the U.S. National Security Council, says the Iranian government is showing signs of uncertainty and anxiety.

"I think what these elections show is the insecurity of the regime," he said. "I think it is a surprising level of insecurity. The regime is obviously very interested in its own survival. And I think, in a sense, we can conclude that the confidence they had was shaken by the events leading up to the election and caused them to take, I think, what everyone agrees is a pretty brazen and transparent act to manipulate the results."

U.S. President Barack Obama says he is very concerned about the election and the suppression of peaceful dissent. He says the United States should not be seen as "meddling" in the dispute.

Despite the protests, Mr. Obama says he is sticking to his policy of seeking a dialog with the Iranian government.

"The use of tough, hard-headed diplomacy - diplomacy with no illusions about Iran and the nature of the differences between our two countries - is critical when it comes to pursuing a core set of our national security interests," he said.

President Obama says those security interests include preventing Iran from obtaining nuclear weapons and for providing support to international terrorists.

Analyst Mehdi Khalaji says he does not expect domestic opposition to Iran's election results to end soon. And he foresees major changes in Iran.

"This is not something that can be ended very soon," said Khalaji. "Nobody can predict where it exactly leads. But what we can say is that something has been changed forever. We are going to face a military government in Iran, a Saddam Hussein-like government or we are going to have tremendous changes in the political system in Iran."

Facing its biggest crisis since the 1979 revolution, Iran's Islamic government has gone on the offensive.

Authorities are trying to block foreign media coverage of the demonstrations and human rights groups say numerous opposition figures have been arrested in recent days.