Iran in turn vowed ‌to shut down all oil exports from the Gulf "if the economic war continues." US Treasury Secretary Scott Bessent will hold a press conference at 1 p.m. EDT on Monday.

"At dawn begins an economic D-Day — the single greatest financial offensive ​ever marshalled against an adversary," Bessent wrote in an opinion piece published in the Financial Times on Sunday.

Iran has been bracing for the sanctions for days, issuing a series of strongly ​worded statements hinting at a major military response.

Mohsen Rezaei, secretary of Iran's Supreme National Security Council, on Sunday suggested economic retaliation. "If the economic war continues, not a single drop of ‌oil will ⁠be exported, neither through the Strait of Hormuz nor from anywhere in the Persian Gulf," Rezaei wrote in a social media post. He added that Iran will regard any country’s participation in or support for America’s economic war against the Iranian people as an act of war.