Today marks the climax of the Ten-Day Dawn commemorating the period between February 1, 1979 when Imam Khomeini returned from exile and the anniversary of the Revolution that ended 2,500 years of monarchical rule in Iran.
Every year on this day, the nation turns out in droves to highlight support for the Revolution which replaced the US-backed regime with an Islamic Republic.
Demonstrators in many cities have braved the cold weather as they descended on main crossroads to renew their allegiance to the country's Islamic principles at a time of rising economic and political pressure.
Last year, the United States unilaterally abandoned an international nuclear pact with Iran and reimposed its toughest sanctions ever, in a move which is viewed as a regime change attempt against the Islamic Republic.
US National Security Adviser John Bolton had said the outcome of the country's policy review should be to determine that Iran's Revolution would not last until its 40th birthday. "And that’s why, before 2019, we here will celebrate in Tehran!” he had told a convention of the terrorist MKO group in Paris in 2017.
Hundreds of thousands of people have headed to the iconic Azadi (Freedom) Square in Tehran amid chants of "Death to America," where President Hassan Rouhani is due to deliver a speech to the nation.
Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei is expected to make an "important" address in the coming days, media reports said on Sunday.
He is set to publish "a detailed statement explaining the 'second step' of the progress of the Islamic Revolution," the website of the Leader said.
Ayatollah Khamenei said on Friday the Iranian nation will keep chanting "Death to America" as long as the United States remains evil.
“The US is the embodiment of evil, but still complains why you chant ‘Death to America’,” the Leader said, referring to President Donald Trump's remarks last week.
Trump said Iran "chants death to America and threatens genocide against the Jewish people," adding "We will not avert our eyes from" the Islamic Republic.
“Death to America means ‘death’ to you, the few people ruling the country; we don’t mean the American nation,” Ayatollah Khamenei said.
US officials have adopted an extremely hostile policy toward Iran under the Trump administration, with Secretary of State Mike Pompeo pledging to “starve” Iranians until they give in to American demands.
Washington is calling for new negotiations which would include restraining Iran's missile program and its role in the Middle East as well as the country's support for anti-Israeli resistance movements, such as Hezbollah.
Iranian officials have stressed that the country would not negotiate its missile capability under any circumstances.
In recent days, the country has unveiled new missiles to highlight its latest achievements on the anniversary of the Islamic Revolution.
Among them are the Dezful precision-guided missile, which is being produced at a secret underground plant, and the cruise missile Hoveizeh.
Israeli experts have concluded that Hoveizeh, which has a range of over 1,300 kilometers, is essentially unstoppable as none of the existing missile defense systems in the world can trace it.