US Attorney General William Barr has said that President Donald Trump "undercuts" him by tweeting, making it "impossible for me to do my job".

His criticism of Mr Trump comes amid intense scrutiny of the Justice Department over the handling of a case involving Roger Stone - a convicted former advisor to the president.

The attorney general had been accused of bowing to presidential pressure.

Mr Barr's comments are a rare sign of annoyance with Mr Trump.