Trump laments Flynn's lies to FBI about Russia contacts: 'There was nothing to hide!'

President Trump on Saturday lamented that his former national security adviser, Michael Flynn, lied about his conversations with Russia’s ambassador after the 2016 election, arguing there was nothing improper about those interactions.

“There was nothing to hide!” the president tweeted Saturday, a day after Flynn pleaded guilty to lying to the FBI about his conversations with Russia's ambassador, Sergey Kislyak, in December of last year.

Trump said he fired Flynn because he lied about those conversations – which were about the Obama administration’s sanctions on Russia -- to Vice President Pence and the FBI.

“He has pled guilty to those lies,” Trump said. “It is a shame because his actions during the transition were lawful.”

TRUMP SAYS ‘NO COLLUSION’ WITH RUSSIA IIN FIRST PUBLIC COMMENTS SINCE FLYNN’S GUILTY PLEA

The president’s tweet was also notable in that it suggested he knew Flynn lied to the FBI when he fired him, something Trump had not previously said. 

Flynn’s guilty plea follows his decision to strike a deal with Robert Mueller’s investigation into the Russia’s attempted interference in the election.

His plea to a single felony count of false statements made him the first official of the Trump White House to be charged so far in the criminal investigation by special counsel Mueller.

The plea turns Flynn into a potentially key government cooperator as prosecutors examine whether the Trump campaign and Russia worked together to influence the election in Trump's favor.

The conversations detailed by prosecutors between Flynn and Kislyak took place after the election but before Trump’s inauguration.

If the Trump transition made secret back-door assurances to Russian diplomats, that could potentially run afoul of the Logan Act, a 1799 law that bars private American citizens from attempting to intervene in “disputes or controversies” between the United States and foreign powers without government approval.

In his first comments since the Flynn plea, Trump told reporters Saturday morning that “no collusion” occurred between Russia and his 2016 presidential campaign.

“No collusion,” Trump said in brief comments from the White House South Lawn before departing for New York. “There was absolutely no collusion. So we are very happy.”

Friday's developments don't resolve the paramount question of possible Trump-Russia coordination in the campaign, but they do show that Flynn lied to the FBI about multiple conversations last December with the Russian ambassador to the United States.

Court papers make it clear that senior Trump transition officials were fully aware of Flynn's outreach to Russian officials in the weeks before the inauguration.

The officials were not named in court papers, but people familiar with the case identified two of them to The Associated Press as Jared Kushner, the president's son-in-law, and former Deputy National Security Adviser KT McFarland, now up for an ambassadorship.

Fox News’ Joseph Weber and The Associated Press contributed to this report.

Alex Pappas is a politics reporter at FoxNews.com. Follow him on Twitter at @AlexPappas.