The statement, released on Saturday morning, said it had done so due to "human error".
Those responsible would be held accountable, the statement read on state TV said.
Iran had previously rejected suggestions that one of its missiles brought down the plane near the capital, Tehran, on Wednesday.
The crash of Ukraine International Airlines flight PS752 with the loss of 176 lives came just hours after Iran carried out missile strikes on two airbases housing US forces in Iraq.
US media have speculated that the airliner may have been mistaken for a warplane as Iran prepared for possible US retaliation.