The Ukraine Airlines flight which crashed in Tehran killing 176 people on Wednesday was shot down by an Iranian anti-aircraft missile system, Pentagon officials have said in a report by Newsweek.
Ukraine International Airlines Flight 752 was struck by a Russia-built Tor-M1 surface-to-air missile system, the magazine reported, quoting three security officials.
Two of the officials said the aircraft was likely targeted by mistake by Iranian missile system as Iran awaited a possible counter-strike after sending rockets to two US bases in Iraq as retaliation for the killing of general Qasem Soleimani.
The aircraft was a Boeing 737-800, bound for Kiev.
It came down in a blaze just three minutes after takeoff, crashing in the outskirts of the Iranian capital.
The timing of the crash has been questioned as tensions escalate between Washington and Tehran.
Canadian officials said 138 of the 167 passengers took the plane to connect flights to Canada.
There were 63 Canadians on the plane and 82 Iranians, 10 Swedes, 3 Brits.
Iran has yet to respond to the latest claim by the US.