The U.S. Commerce Department on Monday issued a rare emergency order aimed at blocking the illegal re-export of two large, used U.S.-built commercial jet engines to Iran by a company based in Turkey.

Assistant Commerce Secretary David Mills, who oversees export enforcement, signed the order on Friday after learning that Turkish-based 3K Aviation Consulting & Logistics planned to re-export two engines built by General Electric Co to Iran on Tuesday using Pouya Airline, an Iranian cargo airline.

There has been a warming in U.S.-Iranian ties this year, including a Nov. 24 deal to curb the Iranian nuclear program, but most exports to Iran remain strictly banned under U.S. law.