William Barr, right, has been seen as an ally of Donald Trump [Source: BBC]

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 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.

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

Barr said “I cannot do my job here at the department with a constant background commentary that undercuts me,” .