US President Donald Trump on Saturday shrugged off the bombshell news that his former national security adviser has pleaded guilty to lying to the FBI and will cooperate with a special prosecutor leading a probe into Russian election meddling. As the Russia probe overshadowed his big win with Senate passage of landmark tax cuts, Trump again insisted he and his campaign had not colluded with Russia. But Trump also suggested he has been holding back something important regarding what he knew at the time of ex-security adviser Michael Flynn 's firing.