U.S. military will start a blockade of the Strait of Hormuz at 10 a.m. ET Monday for vessels linked to Iranian ports.
President Donald Trump is weighing limited strikes on Iran after failed negotiations, while Iran threatens retaliation and calls the blockade piracy.
Oil prices rose above $100 per barrel and global equity markets wavered following the announcement.
U.S. Vice President JD Vance led talks in Pakistan, but Iran refused U.S. demands on nuclear restrictions, keeping ceasefire fragile.