LOS ANGELES: Elon Musk's much-trailed interview with Donald Trump got off to a rocky start on Monday after what the controversial entrepreneur said was a cyber attack on his social media platform.

What was billed as a "no limits" conversation started more than half an hour late, with many people unable to listen in live, in an embarrassing setback for both men.

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

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

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.

But apparent technical difficulties - which come after Musk fired swathes of staff - also served as a reminder that the Tesla boss had once backed Trump rival Ron DeSantis, whose campaign launch on the platform was also beset by problems.

"We tested the system with 8 million concurrent listeners earlier today," Musk wrote.

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 Republican posted multiple campaign ads under his @realDonaldTrump handle on Monday, as well as links to his website.

Musk, the world's richest person according to Forbes, has emerged as a major voice in US politics, but is accused of turning X into a megaphone for right-wing conspiracy theories.

He is one of the Democrats' fiercest critics, leveraging his 194 million-strong following on X to assail liberal efforts to boost diversity and inclusion - what he calls the "woke mind virus" - and the White House's handling of the southern border.

He frequently spreads far-right misinformation about undocumented immigrants and voter fraud.

Trump, meanwhile, is struggling to pivot in the face of surging enthusiasm and strong polls for Kamala Harris since she took over from Biden as the Democratic candidate.

The conversation was never expected to be challenging; the previously rocky relationship between the tech tycoon and the Republican nominee has been transformed, tracking Musk's rise to hero status among young men aligned with Trump's views.

It is this audience, which does not watch rallies or tune in to conservative cable news, that Trump hopes to woo.

Trump, 78, also took part in an interview last week with internet influencer Adin Ross -- who has been repeatedly banned from streaming site Twitch for policy violations.

'Greater responsibility'

X is juggling multiple federal investigations, giving Musk common cause with Trump, who faces more than a dozen felony charges over his efforts to overturn the result of the 2020 election.

Musk has become increasingly focused on priorities shared with the Republican hard-right, voicing anger over supposed censorship of conservatives and spreading inflammatory and false news stories about immigration.

New analysis from the Center for Countering Digital Hate shows that Musk's false or misleading claims about the US elections have been viewed nearly 1.2 billion times on X.

The European Union, which is investigating X under laws requiring digital firms to properly police online content, wrote to Musk Monday to remind him of his legal duty to stop "harmful" material from spreading on the platform.

"With great audience comes greater responsibility," the bloc's top digital official Thierry Breton posted on the platform, along with the letter laying out Musk's obligations to combat illegal content and disinformation under EU law.

Musk mocked Breton, saying the official reminded him of a French character from 1975 British comedy movie "Monty Python and the Holy Grail."

He then responded again, this time with a meme based on the 2008 US comedy movie "Tropic Thunder" that carried an obscene message.

Trump campaign spokesman Steven Cheung accused the EU of election interference and told it to "mind their own business."

"Let us be very clear: the European Union is an enemy of free speech and has no authority of any kind to dictate how we campaign," he said.