The new report is a correction from an earlier story published by NBC News that said federal investigators had wiretapped Cohen.

NBC issued an on-air correction late Thursday afternoon, citing three senior U.S. officials as saying it was not a wiretap. NBC says investigators were actually using a "pen register" that logged phone calls made from specific phone lines.

The network said in an editors note that it was changing the headline and parts of the original story.

The news could raise the legal stakes for Trump, though the revelation that it was not a wiretap lowers them and represents a damaging mistake by a big player in the news media.

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Josh Blackman, a constitutional law professor at the South Texas College of Law in Houston, said it’s far easier to obtain a pen register than a wiretap.

“While the latter records phone calls and captures private information, the former only tracks phone numbers dialed,” he said. “The Supreme Court has recognized that by dialing a phone number, a person voluntarily shares that information with the phone company, so there is a reduced expectation of privacy."

NBC said that at least one phone call between the White House and a line associated with Cohen was monitored. It reported that it was not clear how long the monitoring had taken place. The use of the pen register would not record any of the conversation on the calls.

Cohen's offices and residences were raided by the FBI last month as part of an investigation into Trump's personal lawyer.

Trump was infuriated by that raid, accusing the Justice Department of carrying out a “witch hunt” and an “attack on our country” while asserting the FBI "broke in" to Cohen’s home, office, hotel room and safe deposit box.

The president reportedly called Cohen to check in after the raid. Former New York City Mayor Rudy Giuliani, Trump’s personal lawyer, learned of the call days later and warned Trump not to call Cohen again because he feared he could be under surveillance, according to two sources who spoke to NBC.

Giuliani reacted angrily to the NBC's initial report during an interview with The Washington Post.

“It’s not appropriate,” he said. “I mean, he’s a lawyer. You mean, I call up my lawyer and the government is wiretapping him? That’s pretty damn — I mean, they’ve already eviscerated the attorney-client privilege. This would make a mockery of it.”

The report that Cohen's calls were being monitored comes at a time when Trump’s legal troubles are deepening, causing the president to reshuffle his team of attorneys in order to push back harder against Mueller, who is leading the Russia investigation, and the Justice Department.

Giuliani said on Fox News on Wednesday night that Trump reimbursed Cohen for the payment, a claim he believed could limit the president’s legal exposure in the probe but also contradicted past claims by Trump that he knew nothing about the arrangement.

Citing two sources, NBC reported Giuliani told Trump that Cohen is likely to flip on him and cooperate with investigators. But Trump disagreed, saying that Cohen has been loyal to him for years.