Roughly 20% of global oil consumption passes through the Strait of Hormuz, according to the U.S. Energy Information Administration.
The U.S. Navy's Fifth Fleet, based in Bahrain, is the primary American force patrolling the Persian Gulf and Strait of Hormuz.
Iran has threatened to close the Strait of Hormuz multiple times since the 1980s Tanker War, when the U.S. Navy escorted Kuwaiti tankers under Operation Earnest Will.
A naval blockade is considered an act of war under customary international law and typically requires congressional authorization under the War Powers Resolution of 1973.
U.S. sanctions have already cut Iran's oil exports dramatically from a 2018 peak of about 2.5 million barrels per day, according to the Energy Information Administration.