The US imposed sanctions on Chinese and other companies on Monday after accusing them of helping to sell tens of millions of dollars’ worth of Iranian oil and petrochemical products to East Asia. The move comes as Washington seeks to increase pressure on Tehran to curb its nuclear programme.

The US Treasury and State Departments imposed sanctions on a total of six companies: one in the UAE, four in Hong Kong and one in Singapore. The measures were announced in separate statements.

The US Treasury accuses the Persian Gulf Petrochemical Industries Company of Iran, one of the country’s largest petrochemical brokerages, of using these companies to facilitate the sale of Iranian petroleum and petrochemical products to East Asia. It is said to use the companies’ bank accounts, along with those of Hong Kong and Malaysia-based BZNFR Trading Limited, to raise millions of dollars in revenue.

The UAE-based Blue Cactus Heavy Equipment and Machinery Spare Parts Trading Company is said by the US to have helped sell millions of dollars’ worth of Iranian petroleum products to Hong Kong-based Triliance Petrochemical Company. The latter has been sanctioned by the US in the past. Hong Kong-based Farwell Canyon HK and Chicovi International Trading have also been sanctioned for allegedly facilitating the shipping of these products to buyers in East Asia.

The US State Department, meanwhile, has imposed sanctions on Singapore-based Pioneer Ship Management Services for allegedly operating a vessel carrying Iranian petroleum products, and Hong Kong-based Golden Warrior Shipping Company for alleged transactions related to Iranian oil and petroleum products.

These measures freeze any US-based assets and generally prohibit Americans from doing business with the companies. Anyone who engages in certain transactions with them also risks sanctions. The measures are the third round of US Iran-related sanctions on Chinese companies in the past two months.

Since taking office last year, US President Joe Biden has been reluctant to punish Chinese companies involved in the oil trade with Iran in the hope of reaching an agreement to revive the 2015 Joint Comprehensive Plan of Action (JCPA) nuclear deal with Iran. Efforts to revive the deal, under which Iran imposed restrictions on its own nuclear programme in exchange for relief from US and other sanctions, have so far failed, prompting Washington to look for other ways to put pressure on Tehran.

“The United States continues to pursue the path of diplomacy to achieve a mutual return to full implementation of the JCPA,” said Under Secretary of the Treasury for Terrorism and Financial Intelligence Brian E Nelson. “Until such time as Iran is ready to return to full implementation of its commitments, we will continue to enforce sanctions on the illicit sale of Iranian petroleum and petrochemicals.”

Commenting on the new sanctions, Iranian Foreign Ministry spokesman Nasser Kanaani said that Iran would respond “strongly and firmly” to the White House’s continued imposition of sanctions on the Islamic Republic.