US President Donald Trump today said, his former national security adviser Michael Flynn has pleaded guilty to lying to the FBI and will cooperate with a special prosecutor Robert Mueller who is leading a probe into Russian election meddling. US President Donald Trump told reporters in Washington that there has been absolutely no collusion between his election campaign and Russia.<br/><br/>Mr Trump said he was not worried by what Flynn might tell Mueller. Trump also insisted that Flynn had done nothing wrong during the transition.<br/><br/>US president said, he had fired Flynn in February, just three weeks into the job, because he had lied to Vice President Mike Pence and the FBI about contacts he had with the former Russian ambassador Sergey Kislyak.<br/><br/>Trump's ties with Flynn have been under intense scrutiny since former FBI director James Comey was fired by the president in May. The move led the Justice Department to appoint Robert Mueller as the special prosecutor to probe Russian election meddling.