A gas station is seen in March 2022 in China, which has remained the key buyer of Iranian oil despite US sanctions - Copyright AFP/File Niklas HALLE'N The United States on Thursday imposed sanctions on Iranian petrochemical producers as well as Chinese and Indian brokers, expanding pressure amid a deadlock in negotiations on restoring a nuclear deal. President Joe Biden’s administration said that it still remained committed to diplomacy with Iran to restore a 2015 agreement on curbing its nuclear program. “Absent a deal, we will continue to use our sanctions authorities to limit exports of petroleum, petroleum products and...