Washington announced on Thursday it had removed sanctions on three former Iranian officials and two companies that previously traded Iranian petrochemicals, a step one U.S. official claimed routine but that could show US readiness to relax sanctions when justified.

Speaking on condition of anonymity, a US official said that the moves by the Treasury's Office of Foreign Assets Control (OFAC) were unrelated to efforts to revive Iranian and Washington compliance with the 2015 Iran nuclear deal.

"Today, OFAC and the Department of State are also lifting sanctions on three former Government of Iran officials, and two companies formerly involved in the purchase, acquisition, sale, transport, or marketing of Iranian petrochemical products," the US Treasury said in a statement.