The United States reimposed international sanctions on Iran that the United Nations lifted in 2016 as part of the nuclear agreement, or Joint Comprehensive Plan of Action (JCPOA). However, France, Germany, and the United Kingdom, as well as Iran, said that the reimposition lacked legal validity because the United States is no longer a party to the agreement. The United States threatened to use domestic authorities to punish countries that fail to enforce the U.N. sanctions. The U.S. move is a response to a failed effort by the United States to extend a U.N. arms embargo on Iran set to expire on October 18.

The United States charged three Iranians with hacking aerospace and satellite companies to steal data for the Islamic Revolutionary Guard Corps (IRGC). The U.S. Department of Justice accused Mohammad Bayati, Mohammad Reza Espargham, and Said Pourkarim Arabi of disguising themselves as academics or company representatives in order to trick actual company employees into downloading computer viruses. According to the Justice Department, the trio planned to target 1,800 accounts in Australia, Israel, Singapore, the United Kingdom, and the United States. While U.S. authorities described all three individuals as having IRGC ties, U.S. authorities alleged that Arabi worked as an IRGC operations manager and lived in IRGC housing. The charges followed two earlier indictments of Iranian hackers and coincided with the U.S. Treasury Department's announcement that it was sanctioning a separate Iranian hacking group known as "APT39."

Ali Akbar Salehi, the head of the Atomic Energy Organization of Iran (AEOI), announced that Iran has 1,044 centrifuges enriching uranium at the Fordow plant and that the uranium produced there will be stockpiled. Under the Joint Comprehensive Plan of Action (JCPOA), Iran had pledged to refrain from enriching uranium at Fordow. After the United States withdrew from the JCPOA and reimposed sanctions on Iran, however, Iran began reneging on some of its JCPOA commitments.

Ali Akbar Salehi, head of the Atomic Energy Organization of Iran (AEOI), announced that Iran had begun construction of a new building for centrifuge production in the mountains near the Natanz nuclear complex, Iran's primary uranium enrichment facility. Salehi described the new building as "more modern, wider, and more comprehensive" than Natanz. The development of the new site follows a July 2 explosion at Natanz, which damaged an advanced centrifuge development and assembly plant. An Iranian news agency has linked the explosion to Ershad Karimi, a contractor at Natanz. Karimi owns a company called Mehr that supplies precision measuring equipment.