The U.S. Treasury Department on Thursday imposed sanctions on a network of front companies and agents involved in procuring aluminum products for designated companies associated with Iran’s nuclear program.

The sanctions on Thursday mark the latest escalation in U.S. pressure on Iran since its exit in May 2018 from the nuclear deal. They come amid an offer earlier Thursday from Iranian Foreign Minister Mohammad Javad Zarif to accept enhanced inspections of Tehran’s nuclear program, in exchange for the permanent lifting of U.S. sanctions. It also follows a flurry of maritime activity on Thursday: Iran said on state TV that it seized a tanker, and President Donald Trump announced that the U.S. Navy shot down an Iranian drone over the Strait of Hormuz.

Earlier this year, Tehran responded to the U.S. exit by announcing its reduction of compliance with the deal, including through the resumption of uranium enrichment beyond the levels allowed under the agreement. Earlier this month, Iran announced it broke through another level of enrichment, but Zarif said this week that the steps taken thus far can be reversed within hours. The U.S. rejects Iran’s nuclear enrichment and has threatened Tehran over its efforts.

“Iran cannot claim benign intent on the world stage while it purchases and stockpiles products for centrifuges,” said Treasury Secretary Steven T. Mnuchin.  

The State Department, in a statement about Thursday’s designations, condemned Iran’s recent nuclear efforts. “There is no credible reason for Iran to expand its nuclear program at this time and in this way other than as a transparent attempt to extort the international community,” the department said.

Though the Treasury doesn’t specify when the deals cited in Thursday’s action took place, the procurement network appears to have shipped material to Iran at least as recently as December 2018, Kharon found. 

Some of the products sought by the network were items subject to a multinational export control regime known as the Nuclear Suppliers Group (NSG), according to the Treasury. Under the United Nations Security Council resolution that endorsed the nuclear deal, the sale, supply or transfer to Iran of NSG-controlled items require advance, case-by-case approval from the U.N. -- with narrow exceptions that didn’t apply to Thursday’s action, the Treasury said.

The individuals and entities sanctioned are spread between Iran, China and Belgium, and they’ve acted on behalf of Iran’s Centrifuge Technology Company (TESA), the Treasury said. The U.S. on Thursday designated Mohammad Fakhrzadeh, a TESA commercial director, for coordinating the purchase of various Chinese-origin goods associated with Iranian centrifuge components.

TESA was sanctioned in 2011; it plays a crucial role in Iran’s uranium enrichment program through the production of centrifuges used in facilities belonging to the Atomic Energy Organization of Iran (AEOI), the Treasury said Thursday.

AEOI, the main Iranian institute for nuclear technology research and development, was designated in 2005 when it was listed in the annex of Executive Order 13382, which authorizes sanctions on proliferators of weapons of mass destruction and their supporters. U.S. sanctions on AEOI were removed as part of the nuclear deal, but they were reimposed after the U.S. exit from the agreement. TESA was involved in the production of centrifuges used in the AEOI enrichment plant in Natanz and in facilities at Kalaye Electric Company, a U.S. and U.N.-sanctioned entity linked to AEOI, the Treasury said in 2011.