A bipartisan group of US senators have written to President Joe Biden, urging the administration to enable Homeland Security to seize Iranian oil and gas shipments.

Six democrats and six republicans, led by Joni Ernst (R-IA) and Richard Blumenthal (D-CT), told Biden that the Homeland Security Investigations (HSI) office has not been able to seize Iranian shipments for more than a year.

The DHS program that used to seize illegal Iranian oil, gas and petrochemical shipments had confiscated $228 million worth of fuel linked to the Revolutionary Guards’ extraterritorial Quds Force -- a designated Foreign Terrorist Organization and an arm of the Islamic Republic that continues to sponsor attacks on US citizens and servicemembers -- from 2019 until fiscal year 2022, when the Treasury cut off its funds. HSI's enforcement has been curtailed by policy limitations within the Department of Treasury's Executive Office for Asset Forfeiture.

Referring to the Treasury Department’s acknowledgment in 2020 that “Iranian petrochemical sales remain a key revenue source for the Iranian regime,” specifically the IRGC’s Quds Force, the senators called for bridging the enforcement gaps concerning Iranian petrochemical and petroleum sales. “Enforcement of sanctions against Iranian petrochemical and petroleum sales will defund terrorists' intent on harming the United States and our partners,” read the letter.

“Despite several additional sanctions issued against Iranian petrochemical and petroleum sales over the past year, the volume of Iranian oil exports from Iran from 2021 to 2022 increased by 35%, approximately 430 million barrels of oil, evading sanctions,” they said in the letter.

A few hours after the letter was released, Iran seized a Marshall Islands-flagged tanker in the Gulf of Oman, the latest in a series of seizures or attacks on commercial vessels. "While Iran is seizing ships, our own program is completely languishing," an aide to Ernst told Reuters.