The US was behind some of the cyber attacks intended to disrupt Iran's controversial nuclear programme, according to the New York Times.
President Barack Obama ordered the pace of the cyber war programme, codenamed Olympic Games, to be intensified two years ago amid fears Iran was close to building a nuclear weapon.
The disclosures suggest the US was a key player in the Stuxnet virus, which managed to disrupt up to 1,000 centrifuge machines by sending them spinning out of control. The machines were being used to enrich uranium. It is thought the US would have had help from Israel.
The revelations also raise the prospect the US was responsible for the Flamer virus, which is believed to have downloaded data over two years from Iran's oil industry.