The official said that Iran’s oil exports had already declined to around 1.2 million barrels per day, from 1.8 million barrels per day at the start of the year, after the Trump administration imposed several smaller rounds of sanctions targeting Iran’s oil business.

“We’re still engaging further action to bring that number down even more,” the official said, noting that sanctions pressure during Trump’s first term had cut Iran oil flows to a few hundred thousand barrels per day.

An Iranian foreign ministry spokesperson called the sanctions “a clear example of America’s hostility towards the Iranian nation,” according to the country’s Student News Network.

The spokesperson, Esmaeil Baghaei, also said the oil sanctions represented “an evil act aimed at harming Iran’s economic development and the welfare of its people.”

China is the top buyer of Iran’s oil.

The European Union sanctioned Shamkhani earlier in July, citing his role in the Russian oil trade.

A U.S. official said that Wednesday’s action would impact both Russia and Iran, but the action was focused on Iran.

“From our perspective, given where this individual fits, given his connection to the Supreme Leader and his father’s previous sanctions activities, given the Iran-related authorities, it’s critically important to emphasize that this is an Iran action that is meaningful and very impactful,” the official said.

Ali Shamkhani, Mohammad Hossein Shamkhani’s father, was sanctioned by the United States in 2020.

The latest sanctions announcement came as prospects for renewed U.S.-Iran diplomacy remained dim in the aftermath of the U.S. bombing of Iranian nuclear sites last month.

Trump warned on Monday that he would order fresh U.S. attacks should Tehran try to restart the nuclear sites the U.S. had already struck.

He also told reporters Iran has been sending out “nasty signals” and that any effort to restart its nuclear program would be immediately quashed.

The United States held five rounds of talks with Iran prior to its airstrikes in June, which Trump said had “obliterated” a program that Washington and its ally Israel say is aimed at developing a nuclear bomb.

Some experts have questioned the extent of the damage. Iran denies seeking a nuclear weapon.

A senior White House official said last week that Washington was open to talking directly to Iran. But European and Iranian diplomats have said there is little prospect of Iran re-engaging with the U.S. at the negotiating table for now.