President Donald Trump has condemned his former lawyer Michael Cohen amid US media reports that he secretly recorded Mr Trump discussing payments to former Playboy model Karen McDougal.
The tapes were reportedly discovered during an FBI raid on Mr Cohen's property earlier this year in New York.
Mr Trump tweeted that such a raid was "almost unheard of".
He added that a lawyer secretly recording a client was "totally unheard of and perhaps illegal".
The president also insisted he had done nothing wrong.
Mr Cohen's lawyer responded by saying that Mr Trump's statement was "false".
Inconceivable that the government would break into a lawyer’s office (early in the morning) - almost unheard of. Even more inconceivable that a lawyer would tape a client - totally unheard of & perhaps illegal. The good news is that your favorite President did nothing wrong!— Donald J. Trump (@realDonaldTrump) July 21, 2018
What is the tape said to reveal?
The New York Times reports that in the recording, Mr Trump and Mr Cohen discuss paying Ms McDougal, who says she had a 10-month affair with Mr Trump in 2006, a year after he married his current wife Melania.
The tape was reportedly made two months before the November 2016 election that saw Mr Trump become president.
In the lead-up to the vote, Ms McDougal sold her story to the National Enquirer magazine, which is owned by a personal friend of Mr Trump.
She says a $150,000 (£115,000) agreement gave the tabloid exclusive story rights and banned her from talking publicly about the alleged affair. But the Enquirer did not publish her story after paying for the rights.
Why is this an issue?
The Department of Justice is looking into alleged hush money paid to women who claim they had a relationship with Mr Trump.
It is suggested that such payments, if proved, would amount to an election expense.
Failing to declare election expenses is a crime.
Federal investigators have reportedly demanded the tabloid's records on the McDougal payment.
In May, President Trump admitted that he had reimbursed Mr Cohen for a payment he made to another woman to hush up her claims of an affair.
Mr Trump had previously denied all knowledge of the $130,000 payment to porn actress Stormy Daniels as part of a non-disclosure agreement.
What does Cohen say about the tape?
Mr Cohen, who has not been charged with any crime, is reportedly under investigation for possible bank and tax fraud, as well as potential violation of election law.
He has declined to comment publicly on the tape story.
But his lawyer, Lanny Davis, said in a brief statement on Friday that he was "sensitive" to the ongoing investigation before adding: "Suffice it to say that when the recording is heard, it will not hurt Mr Cohen.
"Any attempt at spin cannot change what is on the tape."
On Saturday Mr Davis responded to Mr Trump's tweet by criticising the president and his lawyer, Rudy Giuliani.
The strategy of @realdonaldtrump @potus @RudyGiuliani is flawed; just as is #Trump’s false #Twitter statement made against @michaelcohen212 this morning. Rudy claims the tape is “exculpatory”. Why so angry?— Lanny Davis (@LannyDavis) July 21, 2018
Mr Cohen once famously vowed he would "take a bullet" for Mr Trump, but he told ABC News earlier this month that his loyalty to his family and country came before his old boss.
His comments stoked speculation that he might co-operate with investigators against Mr Trump, although there has been no confirmation so far that he has done so.
What do Trump's people say?
Mr Trump and his aides have consistently denied he had an affair with Ms McDougal, or had any knowledge of any payment to her.
The New York Times reports that Mr Giuliani, Mr Trump's personal lawyer, has confirmed that his client discussed payments to Ms McDougal with Mr Cohen as per the recording - but that ultimately no such payment was made.
According to the newspaper, Mr Giuliani said the recording was less than two minutes long and that Mr Trump did not know he was being recorded.
It also reports that Mr Giuliani said there was no indication on the tape that Mr Trump knew before the conversation about the payment by the National Enquirer's parent company, American Media Inc, to Ms McDougal.
"In the big scheme of things, it's powerful exculpatory evidence," the Times quotes him as saying.
Is secret recording allowed?
New York state law allows one party to a conversation to tape it without the other knowing.
The New York Times reports that Mr Cohen, while working on behalf of Mr Trump, frequently taped conversations with journalists, other lawyers and business opponents of his client.
It goes on to say that Mr Trump himself also has a history of recording phone calls and conversations.
The ethics of whether lawyers should make such recordings, their legality notwithstanding, is an issue dividing the US legal profession.