Mohammad Nahavandian, President Hassan Rouhani's chief of staff, says cooperation between Iran and Iraq in various areas is "essential in view of common interests, capacities and threats." Nahavandian made the remarks in a meeting with Hojatoleslam Seyyed Javad Shahrestani, representative of Iraq's top Shiite cleric Grand Ayatollah Ali Sistani to Iran, in Qom, ISNA reported on Friday. Shahrestani also said the two countries should use all their potential to boost bilateral ties.