Washington, 7 July 2025 (dpa/MIA) -- US President Donald Trump has hit back at his former adviser, tech billionaire Elon Musk, over plans to form a new political party.

"I am saddened to watch Elon Musk go completely 'off the rails,' essentially becoming a TRAIN WRECK over the past five weeks," Trump wrote on his social media platform Truth Social on Sunday.

"He even wants to start a Third Political Party, despite the fact that they have never succeeded in the United States - The System seems not designed for them."

Earlier on Sunday, Trump told reporters Musk's plan was "ridiculous" and touted the "tremendous success" of the Republicans.

Musk said on Saturday that he had decided to form his own US political party, naming it "America Party."

He made the announcement on his X platform one day after submitting a poll to ask users whether he should create a new party to rival the Democrats and Republicans.

"By a factor of 2 to 1, you want a new political party and you shall have it," wrote Musk. It was not initially clear whether he has taken any formal steps to create the new party.

Trump wrote on Truth Social that third parties were only good for "the creation of Complete and Total DISRUPTION & CHAOS."

"We have enough of that with the Radical Left Democrats, who have lost their confidence and their minds! Republicans, on the other hand, are a smooth running 'machine,' that just passed the biggest Bill of its kind in the History of our Country," he added.

Musk supported Trump's election campaign with more than $250 million and led the cost-cutting DOGE team after the January presidential inauguration until late May, carrying out massive job cuts and slashing US government spending.

However, the pair have since fallen out over Trump's "One Big Beautiful Bill," which the president signed into law on Friday.

Critics, including Musk, argue that the bill would lead US debt to balloon in the coming years.