The US slapped sanctions on the governor of the Central Bank of Iran, charging him with aiding the Revolutionary Guard Corps' (IRGC) transfer of millions to Lebanon's Hizballah.
Tuesday's move is the second in a week aimed at the IRGC. The US Treasury also blacklisted a second official at Iran's central bank, as well as Iraq's Al-Bilad Islamic Bank - which it charged with liaising between the IRGC and Hizballah.
The Treasury said central bank governor Valiollah Seif covertly moved "hundreds of millions of dollars" to Hizballah from IRGC via Al-Bilad Islamic Bank.
Tuesday's action seeks to cut off what the US called a "critical" banking network for Iran, and deny those blacklisted access to the global financial system.
"The United States will not permit Iran's increasingly brazen abuse of the international financial system," said US Treasury Secretary Steven Mnuchin.
"The global community must remain vigilant against Iran's deceptive efforts to provide financial support to its terrorist proxies."
On Thursday, the Treasury announced sanctions against a "large scale" currency exchange network serving the Revolutionary Guards, hitting six individuals and three companies at the centre of the network.
At the time, the US singled out the Central Bank of Iran as "complicit" in the operation, foreshadowing Tuesday's action.
Both moves against Iran's central bank come within one week of US President Donald Trump's decision to withdraw from the landmark 2015 nuclear deal. Analysts say it signals a US intent to ramp up pressure on Iran.
According to AFP, US officials are pushing for a "North Korea scenario" in Iran, a reference to severe sanctions that Washington believes brought Kim Jong-un to halt missile and nuclear testing.
But experts have cast doubt on that narrative and whether if true it would apply to Iran.
The head of Al-Bilad Islamic Bank, Aras Habibm, ran in Iraq's election last weekend under Prime Minister Haidar al-Abadi's electoral list. He is expect to win a parliamentary seat.
