Donald Trump has raised the possibility of firing Robert Mueller, the special counsel leading an investigation into possible Russian collusion, after it emerged the FBI raided the office of his personal lawyer.
Michael Cohen, the US president's long-serving personal lawyer, has previously admitted paying $130,000 (£95,000) to porn star Stormy Daniels, who claims she had an affair with Mr Trump.
Mr Trump said the FBI “broke into” Mr Cohen’s New York offices, and described it repeatedly as “a disgrace”.
Mr Trump went on: “It’s a disgrace. It’s frankly a real disgrace. It’s an attack on our country, and what we all stand for.”
The US president also raised the possibility of firing the special counsel, saying: “I think it’s really a sad situation. Many people have said you should fire him [Mueller]. They found nothing.”
The suggestion is significant because firing Mr Mueller would raise questions over whether Mr Trump was attempting to obstruct the Russia investigation.
Obstruction of justice is one of the grounds for impeaching a US president and helped bring down Richard Nixon, the former US president.
Federal prosecutors obtained the search warrant to search Mr Cohen's office after receiving a referral from the special counsel.
On Monday night Mr Trump described the Russia team as “the most conflicted group of people I have ever seen,” wrongly stating that they were “almost all Democrats” and lashed out once again at his attorney general, Jeff Sessions, for recusing himself from the investigation.
Mr Cohen's lawyers called Monday's search "completely inappropriate and unnecessary".
“Today the U.S. Attorney’s Office for the Southern District of New York executed a series of search warrants and seized the privileged communications between my client, Michael Cohen, and his clients,” said Stephen Ryan, his lawyer.
“I have been advised by federal prosecutors that the New York action is, in part, a referral by the Office of Special Counsel, Robert Mueller.”
Mr Ryan said in a statement that his client has cooperated with authorities and turned over thousands of documents to congressional investigators looking into Russian election meddling.
The search is not believed to be connected to the Russia probe, but is thought to have resulted from information Mr Mueller uncovered.
Mr Cohen is reportedly being investigated for suspected bank fraud, wire fraud and campaign finance violations, according to US media.
FBI agents raided Mr Cohen's Manhattan office, home and hotel room as part of the investigation, and seized documents relating to his clients - including Mr Trump - and his personal finances.
Records relating to a 2016 payment by Mr Cohen to adult film star Daniels are thought to be among the documents the officials seized.
Mr Cohen's payment to Stormy Daniels - real name Stephanie Clifford - has come under scrutiny after it emerged it was made just weeks before the 2016 election.
An election watchdog group complained about the payment, arguing it could be classed as an undisclosed campaign contribution, something Mr Cohen denies.
Mr Cohen is reported to have used a home equity credit line to pay Daniels the $130,000 sum. If he lied to obtain credit, he could face felony charges that carry sentences of up to 30 years in prison.
The lawyer has refused to say what the money was for but the White House has repeatedly said Mr Trump "vehemently denies" having sex with Daniels.
Last week Mr Trump said he was unaware of the payment to Daniels.