Dhaka, July 7 -- US President Donald Trump on Sunday slammed former ally Elon Musk's launching of a new political party as "ridiculous," deepening the Republican's feud with the man who was once his biggest backer.

Trump also branded the SpaceX and Tesla tycoon a "TRAIN WRECK" who had gone "off the rails" after Musk said he wanted to challenge the current US political system.

The world's richest man was almost inseparable from Trump as he headed the cost-cutting "Department of Government Efficiency," but they fell out hard over the president's "big beautiful" tax and spending mega-bill.

"I think it's ridiculous to start a third party," Trump told reporters before he boarded Air Force One on his way back to Washington from his New Jerse...