Elon Musk said Monday his much-trailed interview with Donald Trump had been derailed by a cyber attack on his social media platform.

"There appears to be a massive DDOS attack on X. Working on shutting it down," the world's richest man wrote on the platform formerly known as Twitter.

Musk, who has said he previously voted Democrat, has thrown his weight -- and his wealth -- behind Trump since a gunman tried to assassinate the Republican at a rally last month.

Trump was banned from Twitter after a mob of his supporters stormed the US Capitol in January 2021, but Musk reinstated him when he took the platform over and renamed it.

The two men's conversation on Monday was intended to help reinvigorate Trump's stuttering campaign, which has flagged since President Joe Biden dropped out of the race.

Its apparent failure will be an embarrassment to both men.

"We tested the system with 8 million concurrent listeners earlier today," Musk wrote, pledging to host the live conversation with a limited number of listeners and post "the unedited audio" later.