Farhad Parvaresh told Reuters that a draft of the final report has been completed and is being translated and will be sent to ICAO member states in "a couple of weeks".
He stressed that Iran was adhering to international rules on air investigations, known as Annex 13.
Those rules include a recommendation that the final report appears within 12 months, which in this case runs until early January, though many high-profile probes take longer. The deadline has not yet been reached.
The Iranian official’s remarks came after a governing panel at the United Nations aviation agency urged Iran on Friday to accelerate the investigation into the downing of the Ukrainian airliner.
The ICAO said members of its 36-nation council issued the call, nearly 10 months after a Ukraine International Airlines flight was mistakenly shot down by an Iranian ground-to-air missile, killing 176 people.
"We have had several exchanges with the Iranian CAA in which we urged its authorities to expedite the accident investigation," council president Salvatore Sciacchitano told a meeting of the committee, according to ICAO.
Iran mistakenly shot down Ukraine International Airlines Flight 752 shortly after takeoff from Tehran’s main airport. The majority of the victims were Iranian or Canadian, and many were dual nationals.
Despite attributing the crash to technical failure in the initial assessments, Iran ultimately said that the plane had been brought down by a missile fired “unintentionally” due to “human error” after further investigations, according to Press TV.
Iran called it a “disastrous mistake” that happened at a time when air defense forces were on high alert in case the US retaliated against Iranian missile strikes hours earlier on American military bases stationed in Iraq.
Those strikes were carried out in response to the assassination of Iranian Lieutenant General Qassem Soleimani, in a US drone strike near Baghdad airport on Jan. 3.