Read my lips: Trump spotted rehearsing speech in limo

US President Donald Trump presents the picture of supreme confidence - but candid video footage shows he practices his speech just like anyone else.

In intimate footage filmed by a camera operator affiliated with US TV network MSNBC, Mr Trump can be seen rehearsing for his first speech to Congress which was made on Wednesday (NZ time).

For more than 40 seconds, the former real estate mogul can be seen passionately reciting the address to politicians from the Senate and House of Representatives in the back of his presidential car, as MSNBC hosts watch on in total enthrallment.

"If we can read lips we can get the whole speech preview right now," one laughed.

"He has no idea he's on television. They just haven't been around the machinery of media, the mechanics of the [White House's] South Lawn to know this kind of thing is always televised."

At the end of the clip, First Lady Melania Trump can be seen smiling awkwardly at the camera, clearly aware her husband is being filmed.

Mr Trump's speech to Congress focused on the need for a united nation and government, and invited those present to join him in "dreaming big and bold and daring things for our country".