"Any escalation of this situation will undoubtedly bring about consequences," Esmail Baghaei said. "Our hands are not tied." The new head of Iran's top security body warned Sunday that Tehran will see any country's support for the sanctions as an "act of war".

Treasury Secretary Scott Bessent said Monday that new US sanctions aim to block all potential sources of revenue for Iran and told nations to cut economic ties to Tehran or face retaliation.

Bessent said it's "no longer acceptable to operate in the gray spaces" of the conflict.

He did not name what countries could face potential secondary sanctions from the United States, but China, Turkey and the United Arab Emirates are Iran's largest trade partners. "Let there be no ambiguity as to the position of the United States," Bessent told a news conference. "An economic engagement of any kind with this murderous regime will expose those responsible to the full reach of American power."

The expanded sanctions come after weeks of impasse. The United States has not dislodged Iran's grip on the Strait of Hormuz, through which a fifth of the world's traded oil passed before the war started nearly six months ago.

Iran's demands for reopening the strait include lifting the US naval blockade, withdrawing US forces from the region and reparations for damages sustained in the war. It has held separate talks with Oman, on the other side of the strait, on jointly managing the waterway regardless of whether a new deal is brokered with the US.