Donald Trump has told the US Navy to go back to "goddamned steam" to launch jets from its carriers, declaring the new digital system "no good".

The president's comments came as he took a tour of the yet-to-be-commissioned aircraft carrier Gerald L. Ford in Newport News, Virginia, in March.

Recalling the visit in an interview with Time magazine this week, he said he was told the carrier's new electromagnetic catapult did not have enough power.

“It sounded bad to me. Digital. They have digital. What is digital? And it’s very complicated, you have to be Albert Einstein to figure it out,” Mr Trump said.