A senior investigator from Iran is expected to visit Ukraine in coming days and will determine whether a Ukrainian laboratory is suitable to decode black boxes from a plane that crashed last week, a senior Ukraine security official said on Monday.

Oleksiy Danylov, secretary of Ukraine's national security and defence council, told Reuters in an interview that Iran would have the final say on where the black boxes would be decoded.

After days of denying blame, Iran acknowledged on Saturday that it had mistakenly shot down the plane on Wednesday, killing all 176 people on board shortly after it took off from Tehran for Kiev.

Danylov offered an explanation for one of the early sources of confusion over the incident: a statement issued by Ukraine's embassy in Iran on the day of the crash that initially pointed to engine failure as the cause.

He said the statement, which was deleted later on Wednesday and replaced with another statement saying the cause was unknown, had been issued in a bid to gain access to the crash site.

"If we had said straight away that they had shot it down, I am not sure they would have let us go to the wreckage at all, let us do what we were doing," he said.