The United States launched cyber attacks against Iranian missile control systems and a spy network this week after Tehran downed an American surveillance drone, the Washington Post reported on Saturday.
On Thursday, an Iranian missile destroyed a U.S. Global Hawk surveillance drone, an incident that Washington said happened in international airspace. Trump later said he had called off a military strike on Iranian targets to retaliate because the strike could have killed 150 people. Tehran repeated on Saturday that the drone was shot down over its territory and said it would respond firmly to any U.S. threat.
After the drone's downing, Trump secretly authorized U.S. Cyber Command to carry out a retaliatory cyber attack on Iran, said The Post.
The attack crippled computers used to control rocket and missile launches, according to the Post, which cited people familiar with the matter.
The Post said the strikes, which caused no casualties, had been planned for weeks and were first proposed as a response to the tanker attacks.
"This operation imposes costs on the growing Iranian cyberthreat, but also serves to defend the United States Navy and shipping operations in the Strait of Hormuz,” The Post reported citing Thomas Bossert, a former senior White House cybersecurity official in the Trump administration.
U.S. defense officials refused to confirm the reports.
"As a matter of policy and for operational security, we do not discuss cyberspace operations, intelligence or planning," Defense Department spokeswoman Heather Babb told AFP.
The online operation was first reported Friday by Yahoo News.
Tensions are high between the U.S. and Iran once again following Trump's move more than one year ago to leave a multinational accord curbing Iran's nuclear ambition.
On Saturday, Trump said the U.S. would put "major" new sanctions on Iran next week.
Military action was "always on the table," the president said, but he added that he was open to quickly reach a deal with Iran that he said would bolster the country's flagging economy.
"We will call it 'Let's make Iran great again,'" Trump said. He later wrote on Twitter from Camp David: "We are putting major additional Sanctions on Iran on Monday. I look forward to the day that Sanctions come off Iran, and they become a productive and prosperous nation again."
Meanwhile, Iran has denied responsibility for the earlier tanker attacks, and a top military official on Saturday pledged to "set fire to the interests of America and its allies" if the U.S. attacks.
These cyber attacks aren't the first time the U.S. and Iran have dueled online.
The Stuxnet virus, discovered in 2010, is believed to have been engineered by Israel and the U.S. to damage nuclear facilities in Iran.