"We remain prepared because our phase has not begun yet," Gen. Abdel Ghani Asadi said.
According to the official, the forces currently participating in the operation have launched offensives from four directions to surround the city.
"To surround it, but not to enter it. Other forces will deal with the siege," Ghani said, adding that the forces under his command would enter the city once the current stage of the operation had ended.
Fallujah, in the western Anbar province, has been under the control of the Islamic State militant group since 2014. Reports emerged recently that militants from the group, which is banned in many countries worldwide including Russia, began killing residents attempting to leave the city. IS is suspected of planning to use the civilian population as human shields in case of an army siege.