The video, which appears genuine and was apparently taken on November 3 during Biden's visit to California, shows him being asked by a woman to announce that the 2015 Joint Comprehensive Plan of Action (JCPOA) is no longer in effect.
"President Biden, could you please announce that the JCPOA is dead," the woman, who appears to wear a hair ribbon in Iran's flag colors, asks as Biden passes by shaking hands.
"No," Biden replies.
"Why not?" the woman retorts.
"It is dead, but we are not going to announce it," the US leader said. "Long story," he adds.
The woman, and others next to her, urge him to not make deals with the Tehran government.
"They don't represent us," she said. "They are not our government," another added.
"I know they don't represent you. But they will have a nuclear weapon," Biden says, as the video clip ends.
Biden's comments, which the White House did not deny, came as Iran has not bowed to months of pressure to accept the final stipulations of an agreement to revive the JCPOA, which was abandoned by his predecessor Donald Trump in 2018.
Talks to revive the deal have been ongoing in Vienna since April 2021, and at one point early this year Iran and Washington appeared extremely close to a deal.
Since then there has not been any progress, and the European Union's foreign policy chief Josep Borrell warned in September that the parties were actually "diverging."
Asked about the video, White House national security spokesman John Kirby said nobody was questioning its authenticity.
He said Washington still wants to restore the JCPOA, but that doing so is not priority, given the Ukraine war.
"The president's comments are very much in line with everything we've been saying about the JCPOA, which is just not our focus right now," Kirby told reporters.
"There is no progress happening with respect to the Iran deal now. We don't anticipate any progress anytime in the near future," he said.
"We simply don't see a deal coming together anytime soon, while Iran continues to kill its own citizens and is selling UAVs to Russia," he said, making references to Tehran's campaign to repress months-long demonstrations over its treatment of women, and to Tehran's supplying attack drones to Russia for use in Ukraine.