The tweet was the latest in a running commentary on the case from Trump that began Saturday, a day after Flynn pleaded guilty to lying to the FBI about his interactions with a Russian official.
In other tweets Sunday, Trump also seized on news that Peter Strzok — the former top FBI official assigned to special counsel Robert S. Mueller III’s probe of Russian interference in the 2016 election — was taken off that job this summer after his bosses discovered that he and another member of Mueller’s team had exchanged politically charged texts disparaging Trump and supporting Democrat Hillary Clinton. Strzok was also a key player in the investigation into Clinton’s use of a private email server, which ended without charges against her.
“Report: ‘ANTI-TRUMP FBI AGENT LED CLINTON EMAIL PROBE’ Now it all starts to make sense!” Trump wrote, before proceeding to criticize the FBI and promise to bring it back to “greatness” under his administration.
Trump fired Flynn 25 days into his administration for misrepresenting the nature of his conversations with Sergey Kislyak, the Russian ambassador in Washington at the time, to Vice President Pence and other administration officials.
Comey has alleged that the day after that, Trump urged him to be lenient with Flynn, producing notes in which he quoted Trump as saying, “I hope you can let this go.”
Trump stoked the controversy with one of his Saturday tweets, in which he said part of the rationale for firing Flynn was that he had lied to the FBI.
“I had to fire General Flynn because he lied to the Vice President and the FBI,” Trump wrote in that tweet.
But critics pounced Saturday on Trump, arguing that if he knew at the time of his conversation with Comey that Flynn had lied to the FBI and was under investigation, it may constitute an attempt to obstruct that investigation.
“Are you ADMITTING you knew Flynn had lied to the FBI when you asked Comey to back off Flynn?” Walter Shaub, the former head of the U.S. Office of Government Ethics, asked in a tweet Saturday afternoon.
On Sunday, Sen. Mark R. Warner (Va.), the top Democrat on the Senate Intelligence Committee, said Trump should have taken action against Flynn sooner if he already knew that the then-national security adviser had lied to the FBI.
“Well, if he knew that then, why didn't he act on it earlier?” Warner said on CNN’s “State of the Union.” “It raises a whole series of additional questions.”
Warner also told CNN that Flynn being charged with only one count of lying to the FBI suggests that there are “many more stories that General Flynn will have to tell about his time during the campaign and during the transition.”
The Post reported Saturday that Trump attorney John Dowd had drafted the president’s tweet, according to two people familiar with the message. Dowd confirmed that Sunday, saying he had passed along a draft to Dan Scavino, Trump's social media director.
Two people close to the administration described the tweet simply as sloppy and unfortunate.
As Flynn pleaded guilty Friday, he made clear that he is cooperating with Mueller as the latter probes Russian meddling in last year’s election and possible collusion with the Trump campaign.
Flynn’s decision to cooperate with Mueller was widely seen as a sign of increasing legal peril for other White House aides and perhaps Trump himself, as the investigation has expanded beyond potential collusion with Russia to include obstruction of justice and financial crimes.
In an interview Sunday, Sen. Dianne Feinstein (D-Calif.) said it looked to her that “what we’re beginning to see is the putting together of a case of obstruction of justice.”
Appearing on NBC’s “Meet the Press,” Feinstein, the top Democrat on the Judiciary Committee, said she saw that in the indictments of Flynn and three other Trump associates, as well as the “hyper-frenetic attitude of the White House: the comments every day, the continual tweets.”
“And I see it, most importantly, in what happened with the firing of Director Comey, and it is my belief that that is directly because [Comey] did not agree to lift the cloud of the Russia investigation,” Feinstein said. “That’s obstruction of justice.”
The president continued tweeting about Flynn late Saturday. In one message, he complained that it was unfair for Flynn’s life to be “destroyed” for lying to the FBI, arguing that the agency pursued Clinton far less aggressively while investigating her use of a private email server as secretary of state.
Trump’s commentary on the case began Saturday morning, as he addressed reporters before leaving the White House for a fundraising trip to New York.
He said he was not worried about what Flynn might share now that he is cooperating with prosecutors, forcefully asserting that there was “absolutely no collusion” between his campaign and Russia.
On Sunday, as he commented on news about the reassignment of Strzok, Trump also retweeted a pair of posts on the subject written by Paul Sperry, a conservative commentator. One suggested that the current FBI director, Christopher A. Wray, should “clean house” because of the politicization of the agency.
A little later, Trump promised a better FBI under his leadership.
“After years of Comey, with the phony and dishonest Clinton investigation (and more), running the FBI, its reputation is in Tatters - worst in History!” Trump wrote. “But fear not, we will bring it back to greatness.”
Trump also weighed in Sunday on a decision by ABC News to suspend investigative reporter Brian Ross for an erroneous story about Flynn, saying the network should be sued.
Ross told viewers Friday morning that Flynn was prepared to testify that Trump, as a candidate for president, told him to contact Russians.
Later in the day, Ross walked back his report, saying that the source who had provided the initial information for the story later told him that it was as president-elect, not as a candidate, that Trump had asked Flynn to contact Russians.
On Saturday, ABC apologized for a “serious error.”
Ross’s incorrect report prompted a dramatic reaction in the financial markets.
On Sunday, Trump offered a suggestion to those who lost money: “People who lost money when the Stock Market went down 350 points based on the False and Dishonest reporting of Brian Ross of @ABC News (he has been suspended), should consider hiring a lawyer and suing ABC for the damages this bad reporting has caused - many millions of dollars!”
Carol D. Leonnig contributed to this report.