WASHINGTON — President Donald Trump announced on Twitter Wednesday that he has granted a full pardon to his former national security adviser Gen. Michael Flynn.

"It is my Great Honor to announce that General Michael T. Flynn has been granted a Full Pardon," the president wrote on Twitter Friday.

Trump congratulated Flynn and his family: "I know you will now have a truly fantastic Thanksgiving!"

Earlier, Trump told confidants that he planned to pardon Flynn before leaving office, according to multiple reports.

Flynn is the second Trump associate convicted in the Russia probe to be granted clemency by the president. Trump commuted the sentence of longtime confidant Roger Stone just days before he was to report to prison. It is part of a broader effort to undo the results of an investigation that for years has shadowed his administration and yielded criminal charges against a half dozen associates.

Flynn, who served as Trump’s national security adviser for 23 days in early 2017, twice pleaded guilty to lying to FBI agents about his conversations with former Russian Ambassador Sergey Kislyak regarding sanctions imposed by the Obama administration related to Russian interference in the 2016 election.

After spending three years prosecuting Flynn’s case and recommending in January he be sentenced to six months in prison, the Justice Department, directed by Attorney General William Barr, abruptly announced in May it planned to drop the case “after a considered review of all the facts and circumstances of this case, including newly discovered and disclosed information.” 

The Justice Department said it had concluded that Flynn’s interview by the FBI was “untethered to, and unjustified by, the FBI’s counterintelligence investigation into Mr. Flynn” and that the interview was “conducted without any legitimate investigative basis.”

The move raised questions about possible political influence at the DOJ. Federal court Judge Emmet Sullivan is deciding whether to grant the request to withdraw the case. 

The pardon voids the criminal case against Flynn just as a federal judge was weighing, skeptically, whether to grant a Justice Department request to dismiss the prosecution despite Flynn’s own guilty plea to lying to the FBI about his Russia contacts.

The move, coming as Trump winds down his single term, is likely to energize supporters who have taken up the case as a cause celebre and rallied around the retired Army lieutenant general as the victim of what they assert is an unfair prosecution. Trump himself has repeatedly spoken warmly about Flynn, even though special counsel Robert Mueller’s prosecutors once praised him as a model cooperator in their probe into ties between Russia and the 2016 Trump campaign.

The pardon is the final step in a case defined by twists and turns over the last year after the Justice Department abruptly move to dismiss the case, insisting that Flynn should have never been interviewed by the FBI in the first place, only to have U.S. District Justice Emmet Sullivan refuse the request and appoint a former judge to argue against the federal government’s position.

In the months since, a three-judge panel’s decision ordering Sullivan to dismiss the case was overturned by the full appeals court, which sent the matter back to Sullivan. At a hearing in September, Flynn lawyer Sidney Powell told the judge that she had discussed the Flynn case with Trump but also said she did not want a pardon — presumably because she wanted him to be vindicated in the courts.

Outgoing presidents traditionally grant pardons and commute sentences in their final days in office.

Trump, who previously said he fired Flynn weeks into his presidency because he lied to the FBI and Vice President Mike Pence, has since painted the picture that Flynn was an innocent man entrapped by Obama administration officials determined to “take down a president.” Flynn also has been viewed as a victim of political retaliation by many Trump supporters and conservative media figures.

“What happened to General Michael Flynn, a war hero, should never be allowed to happen to a citizen of the United States again!” Trump tweeted on April 30. 

Flynn’s lawyer is Sidney Powell, who was a member of the Trump campaign’s legal team alleging that widespread fraud cost the president reelection. After Powell made a number of wild claims in public, campaign lawyers Rudy Giuliani and Jenna Ellis released a statement Sunday disavowing Powell. 

Powell admitted to Sullivan in September that she and Trump had discussed a possible pardon but said she asked the president not to step in.

The pardon spares Flynn the possibility of any prison sentence, which Sullivan could potentially have imposed had he ultimately decided to reject the Justice Department’s dismissal request. That request was made in May after a review of the case by a federal prosecutor from St. Louis who had been specially appointed by Attorney General William Barr.

The Associated Press contributed to this report.