A prominent U.S. newspaper says U.S. President Barack Obama has been orchestrating secret, sophisticated cyber attacks on Iran's main nuclear facility.

The New York Times cited anonymous sources close to the program who said the order – given just after Mr. Obama took office – a major expansion of America's cyberweapons program.

The Times reported the cyber attack program was begun under former president George W. Bush, who encouraged Mr. Obama to keep it going, and the new president did so.

The main instrument of attack was a computer virus that later became known as Stuxnet. It was infiltrated into the closed computer network that operates much of Iran's main nuclear enrichment facility at Natanz.

The Iranian network had no access to the Internet, The Times reported, and the virus was introduced in a way that is still secret. The account said the U.S. National Security Agency collaborated with Israel on the program.

The virus collected information on how critical Iranian control systems operated, then began a campaign of sabotage – repeatedly starting and stopping the centrifuges Iran was believed to be using to produce weapons-grade uranium, in a way that destroyed the delicate equipment.

The U.S. newspaper said the lengthy article it published Friday was adapted from a forthcoming book by The Times' chief Washington correspondent.

The published account of the computer-virus program said the Stuxnet program, also known as a “worm,” was never supposed to leave Iran's Natanz computer network, but in 2010 it became clear that the program “had broken free, like a zoo animal that found the keys to [its] cage.”

The Times said President Obama expanded the Stuxnet program after it spread outside Iran.

Iran insists its nuclear program is for peaceful use, but the United States, other Western nations and Israel fear that Tehran is covertly developing the ability to produce nuclear warheads. .

Officials at the Pentagon and the White House refused to comment to VOA reporters who asked about the newspaper account, but some experts said it should come as no surprise that the U.S. uses cyberweapons against Iran.

Aaron David Miller, a scholar at the Washington-based Woodrow Wilson Center who has advised both Democratic and Republican administrations, said the cyber attacks appear to be part of a larger covert war, that includes “assassinations, sanctions – the isolation of Iran.”

And Miller said that leads to a larger question.

“If there is no negotiated settlement on the question of enrichment, whether the covert war will morph into an overt one. And that's the great fear.”

Miller said a cyberwarfare strategy might the safest way to deal with the international crisis over Iran's nuclear work – particularly if the alternative would have been a unilateral military strike by Israel.

Still, he says some use of force might become inevitable, based on the Obama administration's stance – and on comments made by Republican presidential hopeful Mitt Romney – that Iran cannot be allowed to acquire nuclear weapons.

“You wonder if we're not drifting – perhaps not this year but very soon after – toward some sort of military confrontation there, too.”

Iran and other Middle Eastern countries say they recently discovered another computer virus, called Flame, which some experts feel is potentially more harmful than Stuxnet. Reports from Iran and elsewhere, however, say antivirus programs are already available to deflect the Flame virus.

The unidentified officials quotes by The Times did not discuss the Flame virus in detail, but they said it was not part of the cyber attack aimed at Iran's Natanz facility.

The Times reported its story was based on interviews over the past 18 months with current and former American, European and Israeli officials involved in cyber security and cyber warfare, as well as outside experts.

Meanwhile, satellite images obtained by a U.S. research group this week suggest Iran may be trying to erase traces of nuclear weapons testing from a key military site.

The U.S.-based Institute for Science and International Security has published images on its website of Iran's Parchin military complex where the purported testing chamber was razed. ISIS said before-and-after satellite images of the site show that Iran has carried out clean-up activities at the site, abnd concluded this raises furthe3r concerns about “Iranian efforts to destroy evidence of alleged past nuclear weaponization activities.”

The International Atomic Energy Agency has been trying to negotiate access to the Parchin site, which Tehran says is used for testing conventional weapons facility.