Donald Trump struggled to pronounce the word “anonymous” as he railed against an unattributed New York Times op-ed that offered a damning evaluation of his presidency.

Taking to the stage to speak to supporters at a rally in Montana on Thursday, Mr Trump stumbled over the word twice as he ranted about the anonymous author of the piece.

The source of the article painted a chaotic picture of life in the White House, claiming staff deliberately obstruct the president at times to prevent him impulsively pursuing damaging policies.

Mr Trump has routinely mispronounced words during public speeches since his entry to politics, including the names of several American states and various foreign nations.

His speech sparked concern last December when he slurred his way through an address about Israel, prompting suggestions he was suffering from a medical or dental problem.

White House press secretary Sarah Sanders dismissed the rumours at the time, claiming the president had been suffering from a “dry throat”.

Donald Trump struggles with speakerphone on call with Mexican president Enrique Nieto

Mr Trump was declared to be in “excellent” health a month later by White House physicians who carried out a routine medical exam, stating he had performed “exceedingly well” in cognitive tests.