A gas flare on an oil production platform in the Soroush oil fields is seen alongside an Iranian flag in the Gulf, July 25, 2005. Photo: Reuters / Raheb Homavandi / File.

The United States on Thursday said it blacklisted two companies based in Hong Kong, one in Shanghai and one in Dubai for helping Iran‘s state-owned National Iranian Oil Company (NIOC) export millions of dollars of goods in violation of US sanctions.

The US Treasury Department said it imposed sanctions on the Hong Kong-based Triliance Petrochemical Co. Ltd and Sage Energy HK Limited, China-based Peakview Industry Co Ltd and United Arab Emirates-based Beneathco DMCC.

The sanctions would freeze all assets held by the companies that fall under US jurisdiction, generally bar US companies and individuals from dealing with them, and potentially subject non-US financial institutions that knowingly facilitate “significant transactions” for them to US sanctions.

In addition, the US government-imposed sanctions on two other companies, Jiaxiang Industry Hong Kong Limited and Shandong Oiwangwa Petrochemical Co Ltd, and two individuals, Ali Bayandrian, who is linked to Triliance Petroleum, and Zhiqing Wang, a Chinese national linked to Shandong Oiwangwa.

The announcements are the latest step in the US “maximum pressure” campaign designed to squeeze the Iranian economy to try to force Iran to accept greater constraints on its nuclear program, regional activities and pursuit of ballistic missiles.

US-Iran tensions have risen since the American decision to abandon the 2015 Iran nuclear deal, its subsequent re-imposition of US sanctions on the Islamic Republic, attacks on Saudi oil facilities blamed on Iran and the US drone strike that killed Iranian military commander Qassem Soleimani in early January.