His remarks drew a swift rebuke from Tehran, where the Islamic Republic's hard-line President Ebrahim Raisi addressed a rally to mark the 1979 takeover of the U.S. Embassy.
The protests that erupted in the wake of 22-year-old Mahsa Amini's death have posed one of the most serious challenges to the theocracy that has ruled the country since the 1979 revolution. They have also triggered support from women and others across the world, with the Biden administration facing growing pressure from Iranian American activists to do more.
"Don't worry, we're gonna free Iran," Biden told supporters in an aside during a campaign speech in California late Thursday, after audience members appeared to call on him to address the ongoing protests. "They’re gonna free themselves pretty soon," he added.
He was speaking at a campaign rally for Democratic Rep. Mike Levin at the MiraCosta College near San Diego. He did not expand on the comment or mention any specific actions the United States might take.
The Biden administration said Wednesday it would try to remove Iran from the United Nations Commission on the Status of Women over its government’s stance on women’s rights, as well as its ongoing crackdown on the weekslong protests.
“Change in Iran should only come from within Iran. But that does not absolve the world of the obligation to stand with the Iranian people as they protest for women, for life and for freedom," the U.S. ambassador to the U.N., Linda Thomas-Greenfield, said echoing the slogan that has been the hallmark of more than six weeks of protests.
Washington has also imposed new sanctions on Tehran over the crackdown and its support for Russia's war in Ukraine.
Iran has rejected international criticism of its response to the protests, denied it has violated the human rights of its people or killed unarmed demonstrators, and has framed the unrest as a Western plot.
Raisi responded directly to Biden's remarks during a televised address Friday, saying "Iran was freed 43 years ago and is determined not to fall into your captivity."
He suggested that Biden’s statement was “probably due to the absent-mindedness that he suffers from."
His comments came as state-sponsored rallies were held across the country to mark the anniversary of the 1979 seizure of the U.S. Embassy in Tehran, which saw students storm the site after the fall of the U.S.-backed Shah Mohammad Reza Pahlavi.
Dozens of Americans were held hostage at the embassy for nearly 450 days, leading to the erosion of diplomatic ties between the two countries, which were then severed in 1980.
Speaking to people gathered in front of the former embassy building, Raisi criticized those protesting against the government.
“Anyone who takes a single action, even if extremely small, as participation in the riots must know that they have taken that action in the desired direction of the enemies of the Islamic Revolution," he said.
The pro-government gatherings were a stark contrast to the wave of nationwide protests in Iran that began Sept. 16 following Amini's death after she was detained by morality police for allegedly failing to comply with the country’s strict dress code.
The U.S. estimates that approximately 280 people have been killed in the protests in Iran as of Nov. 1, according to an official with knowledge of the assessment. The estimate is based in part on open public sources, the official told NBC News.
Two human rights groups, the Norway-based Iran Human Rights and the U.S-based Human Rights Activists News Agency have made similar estimates of the death toll.