The US sanctions slapped Monday on Iran's supreme leader Ayatollah Ali Khamenei and other officials will block "literally billions" in Iranian assets, US Treasury Secretary Steven Mnuchin said.
The sanctions, which US President Donald Trump signed in an Oval Office appearance with Mnuchin, target eight top military commanders as well as Khamenei.
Iran's Foreign Minister Javad Zarif also will be blacklisted "later this week," Mnuchin said.
Some of the sanctions had been planned in advance, while others were added in retaliation for the downing last week of a US Global Hawk surveillance drone, according to Mnuchin.
Trump had considered a military strike after the drone was downed Thursday, then reversed himself minutes before it was to be carried out. He has said he changed his mind after learning that as many as 150 people could be killed.
Among those sanctioned Monday was Iranian Revolutionary Guard naval commander Ali Reza Tangsiri, who the US said had threatened in February to close the Strait of Hormuz, crucial to global oil trade.
Also blacklisted was Aerospace Force commander Amirali Hajizadeh, whom Washington blames for the downing of the drone. Iran says it was shot down after entering its air space, but the US insists it was in international airspace over the Strait of Hormuz.
The sanctions largely freeze their targets out of much of the global financial system, blocking them from US-dollar-denominated transactions and barring international banks from moving money on their behalf while also freezing any assets under US jurisdiction.