US President Donald Trump has said he is 'not worried' about what former National Security Adviser Michael Flynn may now tell investigators about his contact with Russian officials. 

As he left the White House on Saturday, Trump tried to deflect Flynn's shock admission that he had lied to FBI investigators when questioned over the matter and said confidently there had been 'no collusion' between his camp and the Kremlin. 

Asked if he was worried about what Flynn will now reveal, Trump said without a beat: 'No I am not. What has been shown is what has been shown is there's been absolutely no collusion so we're very happy.' 

He refused to say whether or not he would stand by Flynn, saying only: 'We'll see what happens'.

He then tried to steer reporters' attention to Republicans' overnight victory in the Senate where they managed to approve a drastic tax overhaul bill in the early hours of the morning. 

'Frankly, last night was one of the big nights,' said Trump, before making his way on to the South Lawn to board Marine One.