The Trump administration on Tuesday expanded its economic campaign against Iran by imposing sweeping new sanctions on a major shipping and oil trading network just hours after the U.S. military resumed its maritime blockade of Iranian ports.

The U.S. Department of the Treasury’s Office of Foreign Assets Control (OFAC) announced sanctions targeting more than 50 individuals, companies and vessels linked to Iranian businessman Mohammad Hossein Shamkhani, describing the network as one of the country’s largest facilitators of sanctions evasion, oil exports and global shipping operations.

The action came as U.S. Central Command (CENTCOM) confirmed that American forces had resumed enforcing the naval blockade against vessels traveling to and from Iranian ports at 4 p.m. ET.

“There are currently more than 20 U.S. Navy warships and hundreds of military aircraft operating across the Middle East,” CENTCOM said. “American forces remain vigilant, lethal, and ready.”

The sanctions represent one of the largest single actions yet against the Shamkhani network, which U.S. officials say has become a central pillar of Iran’s oil export system while expanding into container shipping and commodities trading.

“The Iranian regime survives on deception, and the Shamkhani network is one of its most profitable engines,” Treasury Secretary Scott Bessent said in announcing the measures. “Treasury is shutting down the financial infrastructure that allows the regime to continue its threats to U.S. national security and global shipping.”

According to Treasury, the latest designations bring the total number of individuals, entities and vessels sanctioned in connection with the Shamkhani network to more than 200.

Among those designated are financiers, shipping executives and vessel managers operating across the United Arab Emirates, Singapore, India, Hong Kong, the Marshall Islands and St. Kitts and Nevis. Treasury also sanctioned a number of shipping management companies and vessel-owning entities that it says helped move Iranian oil, Russian petroleum products and other cargoes while concealing the network’s involvement.

The action significantly expands pressure on the network’s container shipping operations. Treasury designated Singapore-based Sea Lead Shipping PTE. Ltd., several of its subsidiaries and affiliated logistics providers, alleging they enabled both legitimate and illicit cargo movements benefiting the Shamkhani organization, including shipments connected to the Houthis in Yemen. Multiple container ships and tankers were also identified as blocked property under the sanctions.

The new designations build on the administration’s rapid return to its “maximum pressure” strategy. While General License X had temporarily reopened Iranian oil exports and authorized maritime services ranging from vessel management and insurance to bunkering and classification, that policy was effectively abandoned after renewed attacks on merchant shipping earlier this month.

Under U.S. sanctions, all property and interests in property belonging to the designated persons that are within U.S. jurisdiction are blocked, and U.S. persons are generally prohibited from conducting transactions with them. Foreign companies that continue doing business with sanctioned entities also risk secondary sanctions.

The sanctions coincide with the resumption of the U.S. maritime blockade following the collapse of the June ceasefire agreement between Washington and Tehran. The blockade prohibits commercial shipping to and from Iranian ports while allowing neutral transit through the Strait of Hormuz, subject to inspections by U.S. forces.

The blockade had been suspended on June 18 after the Islamabad Memorandum temporarily halted hostilities and eased restrictions on Iranian exports. The agreement unraveled after renewed attacks on commercial shipping in the Strait of Hormuz, prompting the United States to resume military operations and reimpose economic pressure on Tehran.

The combined military and financial measures underscore the administration’s return to its pre-ceasefire strategy of restricting Iran’s maritime trade while maintaining freedom of navigation for international shipping transiting the Strait of Hormuz.