US President Donald Trump has said the actions of former national security adviser Michael Flynn after the 2016 presidential election were "lawful".
Mr Flynn has entered into a plea deal and agreed to co-operate with an inquiry into alleged collusion between Mr Trump's team and Russian officials.
The president said on Twitter that he fired Mr Flynn "because he lied to the Vice President and the FBI".
He said there was "nothing to hide" in the actions of his transition team.
Mr Flynn has pleaded guilty to making false statements to the FBI about meetings with Russia's ambassador Sergei Kislyak in December 2016, after Mr Trump was elected but before he became president.