Michael Flynn, President Donald Trump's former national security adviser, pleaded guilty Friday to lying to the FBI about his postelection contacts with Russia's ambassador to the United States — and is now cooperating with a probe into links between the Trump campaign and Russia.
Flynn surrendered Friday morning before a hearing in Washington federal court, where he admitted guilty to a single criminal count of knowingly making materially false, fictitious and fraudulent statements to FBI agents.
That charge against the retired Army lieutentant general was lodged by prosecutors for special counsel Robert Mueller, who is probing alleged connections between the Trump presidential campaign with Russians.
Mueller's office in a court filing said "Flynn's false statements and omissions impeded and otherwise had a material impact on the FBI's ongoing investigation into the existence of any links or coordination between individuals associated with the Campaign and Russia's effort to interfere with the 2016 presidential election."
At the plea hearing, prosecutors said Flynn had spoken last year with senior members of Trump's transition team about his conversations with the Russian ambassador, which were related to sanctions imposed by the Obama administration.
Specifically, a prosecutor said, Flynn spoke to one senior official who was at Trump's Mar-A-Lago resort property in Florida about what to say to Ambassador Sergey Kislyak.
In a statement after the hearing, Flynn said it had been "extraordinarily painful to endure these many months of false accusations of 'treason' and other outrageous acts."
"But I recognize that the actions I acknowledged in court today were wrong, and through my faith in God I am working to set things right," Flynn said.
"My guilty plea and agreement to cooperate with the Special Counsel's Office reflect a decision I made in the best interests of my family and of our country. I accept full responsibility for my actions."
The charge against Flynn carries a maximum possible prison sentence of five years — but his plea agreement calls for a recommended sentence of no more than six months in prison.
Flynn's son Michael G. Flynn, whose work for his father's consulting group was reportedly being scrutinized by investigators, is not expected to be charged in the case now, a source told The Washington Post.
A leading criminal defense lawyer not connected to the case told CNBC that Flynn's plea is "a very big deal" because it signals Mueller believes information from Flynn will be used to successfully prosecute other Trump associates.
"It's the beginning of the end," said the lawyer, Gerald Lefcourt of New York, a past president of the National Association of Criminal Defense Lawyers.
Flynn is the "key to the whole thing," Lefcourt said.
Trump has denied any improper dealings with Russians.
Speaking of the Flynn developments, Trump attorney Ty Cobb said: "The false statements involved mirror the false statements to White House officials which resulted in his resignation in February of this year."
"Nothing about the guilty plea or the charge implicates anyone other than Mr. Flynn," Cobb said in his prepared statement.
"The conclusion of this phase of the Special Counsel's work demonstrates again that the Special Counsel is moving with all deliberate speed and clears the way for a prompt and reasonable conclusion."
Flynn's plea caps weeks of speculation about his fate and marks a new stage in Mueller's investigation into possible links between Trump's top advisers and representatives of the Russian government before and after the 2016 presidential election.
In late October, Mueller's team charged former Trump campaign chairman Paul Manafort and his business partner Richard Gates for working as unregistered agents on behalf of the pro-Russian government of Ukraine, among other charges.
At the time those charges were announced, it was revealed that ex-Trump campaign foreign policy adviser George Papadopoulos had secretly pleaded guilty to lying to the FBI about his own contacts with Russian agents.
Read the charges against Flynn:
Flynn admitted to falsely claiming he had not asked Kislyak on Dec. 29 "to refrain from escalating the situation in response to sanctions that the United States had imposed against Russia that same day."
Then-President Barack Obama had announced those sanctions along with the expulsion of 35 Russian diplomats in retaliation against the Kremlin for interfering with the 2016 presidential election.
Flynn also admitted lying by investigators "he did not recall the Russian Ambassador subsequently telling him that Russia had chosen to moderate its response to those sanctions as a result of his request," the government said.
Flynn also admitted to stating that he "did not ask the Russian Ambassador to delay the vote on or defeat a pending United Nations Security Council resolution," according to the filing. The resolution, which was approved, condemned Israeli settlements.
Mueller's office said Flynn in March filed multiple documents with the Department of Justice pursuant to the law requiring registration by agents for foreign governments. The documents pertained to a project Flynn's company, the Flynn Intel Group, was doing for the benefit of the nation of Turkey.
In those filings, Flynn lied by falsely claiming his company did not know whether or to what extent Turkey was involved in the project, and other aspects of the deal, according to the special counsel.
The guilty plea comes a week after news broke that Flynn's lawyers had informed Trump's legal team that they could no longer communicate about Mueller's probe.
That shutdown from the Flynn team was taken as a sign that he was cooperating with Mueller's expansive investigation.
Flynn's lawyers met with Mueller's team on Monday.
Flynn and his son have been eyed by Mueller's investigation in connection with a variety of issues, including the elder Flynn's contacts with the Russian ambassador, and the question of whether he tried to orchestrate the potentially illegal removal of a Turkish cleric from the United States in exchange for millions of dollars. That cleric has been a target of Turkish President Recep Tayyip Erdogan.
NBC News reported in early November that sources familiar with Mueller's probe had said the special counsel had assembled enough evidence against both Flynns to indict them on criminal charges.
In addition to Mueller's investigation, Flynn has faced inquiries from the House and Senate, as well as a separate Pentagon probe, for a variety of undisclosed ties to foreign governments.
The first undisclosed contact with a foreign government came in 2015 when Flynn traveled to Russia for the 10th-anniversary dinner for Russian broadcaster RT. Flynn told security clearance investigators that he was paid by American companies for the trip. In fact, he later acknowledged that he signed a $45,000 contract with the Russian state-funded network.
Flynn later found himself in trouble for failing to disclose his work during the Trump campaign for Turkish businessman Ekim Alptekin, which he later said in a filing "could be construed to have principally benefitted the Republic of Turkey."
In a strange twist, Mueller's agents were seeking details about a $15 million deal reportedly hatched in December between Flynn and senior Turkish ministers to deliver the cleric Fethullah Gulen from his exile in Pennsylvania to Turkish custody. Flynn's attorney has called the report "false."
Flynn's tenure in the White House ended after only 24 days because the former Defense Intelligence Agency chief misled Vice President Mike Pence about conversations Flynn had during the transition with Kislyak about U.S. sanctions on Russia. Flynn had previously met the ambassador for a brief meeting at Trump Tower that was also attended by senior Trump adviser Jared Kushner, the president's son-in-law.
Trump has stood by Flynn as the accusations piled up.
The day after Flynn resigned as national security adviser, Trump told then-FBI Director James Comey that Flynn was a "good guy" and suggested that the FBI director let the situation go, Comey told congressional investigators.
"I hope you can see your way clear to letting this go, to letting Flynn go," Trump told him, according to Comey's June testimony to the Senate intelligence committee.
The president has called the investigations into Flynn a "witch hunt."
Flynn and his attorneys had earlier sought immunity for charges related to the investigations.
In March, Flynn's attorney released a statement saying that "General Flynn certainly has a story to tell, and he very much wants to tell it, should the circumstances permit."
The Senate Intelligence Committee later rejected Flynn's immunity request, NBC News reported.
Obama warned Trump against hiring Flynn two days after Trump's election victory, according to The New York Times.