Donald Trump has blamed a teleprompter mishap led to his much-mocked "July Fourth flub" in which he talked about defending airports during the American Revolution.

"The teleprompter went out," the US President told reporters as he left the White House for a weekend at his golf club in Bedminster, New Jersey.

"It just went out – it went kaput."

During his Independence Day speech paying tribute to the military, Mr Trump sowed confusion when he began talking about air defenses during the American Revolution, which took place more than a century before the invention of the airplane.

"Our Army manned the air, it rammed the ramparts, it took over the airports," Trump said of the fighting force created by the Continental Congress in 1775.

There was no air travel in 18th Century America.

Trump, who has derided Democratic opponents like Hillary Clinton for using teleprompters, did make use of one for his big July Fourth speech. But he said the rain foiled its usefulness.

"I guess the rain knocked out the teleprompter," he said. "I knew the speech very well, so I was able to do it without a teleprompter. And it was hard to look at it anyway."

Trump did not explain why, given the failure of the teleprompter, he began talking about airports in colonial America.

Here is Trump's full riff on the American Revolution military:

"In June of 1775, the Continental Congress created a unified Army out of the Revolutionary Forces encamped around Boston and New York, and named after the great George Washington, commander in chief. The Continental Army suffered a bitter winter of Valley Forge, found glory across the waters of the Delaware and seized victory from Cornwallis of Yorktown.

"Our Army manned the air, it rammed the ramparts, it took over the airports, it did everything it had to do, and at Fort McHenry, under the rocket’s red glare it had nothing but victory. And when dawn came, their star-spangled banner waved defiant."

This story first appeared in The Herald's sister paper, USA Today.