It's splittsville for a leading global power couple. Donald Trump and Elon Musk are tumbling into a messy public divorce.

Simmering tension between the erstwhile Oval Office buds bubbled further into open view Thursday, as they exchanged digs in public and their own social media sites.

The world's most powerful elected politician and its richest man had a blowout whose immediate cause is the U.S. federal budget.

Musk has been increasingly disparaging the president's signature budget bill since leaving his unusual government role last week, fuming recently that the bill will plunge the U.S. even deeper into its debt hole, and calling it "a disgusting abomination."

Trump's reply: Musk is just bitter. He suggests Musk is unhappy with parts of the bill that hurt his electric-vehicle business. He also suggests the Tesla billionaire misses the action in the White House.

And because this is Donald Trump's Washington, the chancellor of Germany happened to be seated in the room, witness to one side of the feud.

"Elon and I had a great relationship. I don't know if we will anymore," Trump told reporters during a lengthy photo op Thursday in the Oval Office with Friedrich Merz.

"He's not the first. People leave my administration and they love us. And then at some point, they miss it so badly ... I don't know what it is. It's sort of Trump Derangement Syndrome, I guess they call it," he said.

"They leave, and they wake up in the morning, and the glamour's gone, the whole world is different – and they become hostile. I don't know what it is."

Trump continued escalating the dispute on his own social-media site. On Thursday afternoon, he posted on his social-media platform Musk was "wearing thin," and suggested he'd fired him.

"I asked him to leave," Trump wrote on Truth Social, to which Musk responded on X, formerly Twitter, "Such an obvious lie. So sad."

The president also uttered a thinly veiled threat: Trump wrote that one easy way to trim the federal budget is to cancel government contracts with Musk's companies. "I was always surprised that Biden didn't do it!"

'Without me, Trump would have lost'

Musk, meanwhile, has been using X, the enormous online megaphone he happens to own, to continually broadcast digs at the administration.

He's disputing that his own business interests soured him on the legislation. The bill, which has passed the House but faces an uncertain path in the Senate, eliminates an EV tax credit.

And he's demanding a little more gratitude after he dumped the equivalent of nearly $400 million Cdn into electing Trump and his allies.

"Without me, Trump would have lost the election," Musk posted Thursday on X.

"[Democrats] would control the House and the Republicans would be 51-49 in the Senate."  

Elon Musk gets Oval Office send-off from Trump

U.S. President Donald Trump lauded billionaire Elon Musk’s time heading the Department of Government Efficiency during an event marking the end of Musk’s controversial tenure in the Trump administration.

Hints of trouble in political paradise

It's an abrupt plot twist: The pair were all smiles and praise for each other just last week, as Musk announced his departure from Washington.

But there were hints of trouble behind the scenes. There were occasional reports of blowups between Musk and other members of the administration, and the New York Times reported that sources were concerned about Musk's frequent use of different drugs, including, allegedly, so much ketamine that it was affecting his bladder. Musk denied it.

Now Musk has gone from White House consigliere to chief heckler in under a week — a speed record even for D.C.

As is custom in Trump-era Washington, the human-resources gossip risks overshadowing substantive challenges faced by the U.S. government.

With American debt levels ballooning, and the cost of servicing the national debt recently outpacing even military spending, Musk was tasked with controlling finances.

He slashed countless offices, programs, research initiatives, and even the entire agency that oversaw U.S. international aid.

Still, it put only a modest dent in federal spending: Musk's DOGE project has eliminated an estimated $170 billion US, less than one-10th of the annual budget deficit.