US President Barack Obama accelerated cyberattacks on Iran's nuclear program and expanded the assault even after the Stuxnet virus accidentally escaped in 2010, the New York Times reported Friday.
The operation, begun under president George W. Bush and codenamed "Olympic Games," is the first known sustained US cyberattack ever launched on another country, and used malicious code developed with Israel, the Times said.
The Times said the article was based on 18 months of interviews with current and former US, European and Israeli officials, and was adapted from the book "Confront and Conceal: Obama's Secret Wars and Surprising Use of American Power," by David Sanger, set to be published next week.
The cyberattack, aimed at preventing Iran from developing nuclear weapons and keeping Israel from launching a preventive military strike, sowed widespread confusion in Iran's Natanz nuclear plant, the Times said.
However, top administration officials considered suspending it after Stuxnet -- a complex virus developed jointly with Israel -- "escaped" the facility and began appearing in computer systems in several countries, the Times said.
Obama eventually ordered the attacks to continue, and within a week of Stuxnet's escape a newer version of the bug temporarily brought down 1,000 of Iran's 5,000 nuclear centrifuges spinning at the time, the Times said.
Experts have long suspected that Stuxnet, which targeted computer control systems made by German industrial giant Siemens, was of US and Israeli origin, but neither country has admitted to having a hand in it.
A Pentagon spokesman, Captain John Kirby, declined to comment in detail on the article but said that Obama and Defense Secretary Leon Panetta have put a priority on the cyber realm.
"As we've said many times and the president and secretary made clear, cyber domain is a domain that we need to constantly evaluate and constantly assess and try to improve the range of capabilities that we have in cyberspace," Kirby told reporters.
The United States and Israel have long accused Iran of seeking nuclear weapons in the guise of a civilian program, charges denied by Tehran, which insists its nuclear program is for purely peaceful purposes.
The Times article comes days after experts at Russia's Kaspersky Lab, a top anti-virus software firm, discovered "Flame," a sophisticated virus several times larger than Stuxnet that also seems to have been aimed at Iran.
Explore further: Research reveals we may need a new definition for privacy