WASHINGTON- The United States on Thursday imposed sanctions on five United Arab Emirates-based companies, accusing them of having collectively purchased in 2019 hundreds of thousands of metric tons of petroleum products from Iran.

The U.S. Treasury Department said in a statement the blacklisted companies - Petro Grand FZE, Alphabet International DMCC, Swissol Trade DMCC, Alam Althrwa General Trading LLC and Alwaneo LLC Co - purchased the petroleum products in 2019 from the National Iranian Oil Company for delivery to the United Arab Emirates.

The announcement, which followed the blacklisting of Chinese and South African companies earlier this week over Iran oil trade, seemed a further indication Washington would not ease its campaign of choking off Tehran's ability to export its oil, despite appeals from China and others that it do so on humanitarian grounds because of the coronavirus outbreak.

The U.S. "maximum pressure" campaign, instituted after President Donald Trump in 2018 unilaterally withdrew from the 2015 nuclear deal Iran struck with six major world powers, aims to force Tehran to limit its nuclear, missile and regional activities.

Thursday's sanctions freeze any U.S.-held assets of the companies and generally bar Americans from doing business with them.

"The Iranian regime uses revenues from petroleum and petrochemical sales to fund its terrorist proxies ... instead of the health and well-being of the Iranian people," Treasury Secretary Steven Mnuchin said in the statement.

(Reporting by Daphne Psaledakis and Doina Chiacu; Editing by Chizu Nomiyama and Steve Orlofsky) ((doina.chiacu@thomsonreuters.com; 202-898-8322;))