In a statement of his own, Iran’s foreign minister, Mohammad Javad Zarif, tried to place some of the blame on the United States, saying on Twitter that the disaster was “caused by U.S. adventurism.” The military’s statement said there had been information suggesting the United States was “preparing to aerially target sensitive defense and key sites and multiple targets in our country, and this led to even more sensitive defense posture by our antiaircraft units.”
The State Department had no immediate comment late Friday about Iran’s admission of responsibility.
Suspicions that an Iranian missile had brought down the plane were raised immediately after the crash Wednesday morning — just hours after Iran fired missiles at two bases in Iraq housing American forces.
The Iranians asked the National Transportation Safety Board to help with the investigation, and the State Department granted waivers to allow the American agency to help. A senior administration official said Friday that he thought the Iranians wanted American investigators there to keep up the appearance that they did not know what had caused the crash.
The official, who spoke on the condition of anonymity because he was not authorized to discuss these matters publicly, said the Iranian military had poor command and control, and that this was reflected in what had happened with the airplane. Communications among officials and between units are often lacking, he said, and confusion can be the norm. Western analysts often overestimate the capability of parts of the Iranian military, he said.
State television in Iran aired footage that it said showed two flight recorder units recovered from the crash site. Processing their data could take more than a month, and the investigation could take up to two years, Hassan Rezaeifar, the head of the Iranian investigation team, said Friday.
The military announcement came as something of a surprise. As late as Friday night, officials were weighing whether to blame faulty jet equipment in acknowledging that Iranian missiles brought down the jet, according to four Iranians familiar with the deliberations.
Until Saturday, Ukraine’s main intelligence agency, known as the S.B.U., said only that it had narrowed the cause of the crash to a missile strike or a terrorist act and that it could not confirm Western intelligence that an Iranian missile system was likely to blame.