Donald Trump has responded to a guilty plea by his former national security adviser Michael Flynn, saying Mr Flynn's actions as a member of his transition team "were lawful".
Mr Flynn has entered a plea deal and agreed to co-operate with an inquiry into alleged collusion with Russia.
The deal, for a lesser charge than he might have faced, prompted speculation that he has incriminating evidence.
The president wrote on Twitter on Saturday that he had "nothing to hide," the BBC reports.
Mr Flynn is cooperating with Special Counsel Robert Mueller, who is leading an investigation into alleged ties between the Trump campaign and Russia ahead of the 2016 election.
On Saturday, a day after Mr Flynn's indictment, it emerged that a veteran FBI agent was dismissed from Mr Mueller's team after the discovery that he had sent anti-Trump text messages.
Peter Strzok was removed from the investigation in summer, a spokesman for the special counsel's office, said.
Russia scandal rears its head
Saturday should have been a momentous day for Mr Trump, after his sweeping tax reform bill finally scraped through the senate in the early hours of the morning with 51 votes to 49.
But any celebratory mood among administration officials would have been short-lived - dampened by a string of news reports on the Russia scandal.
In tweeting early on Saturday to deny that Mr Flynn had acted unlawfully as part of his transition team, Mr Trump appeared to admit that he knew the former general had lied to the FBI before he fired him, contradicting the president's account at the time.
Analysts say if Mr Trump knew that Mr Flynn had lied to the FBI, at a time when he appeared to pressure then-FBI director James Comey to drop the agency's investigation into the former general, it could amount to obstruction of justice by the president.
Matthew Miller, a former Obama administration Justice Department official, said in a tweet: "Oh my god, he just admitted to obstruction of justice. If Trump knew Flynn lied to the FBI when he asked Comey to let it go, then there is your case."