WASHINGTON (Reuters) - President Donald Trump threatened on Thursday to cut off government contracts with billionaire Elon Musk's companies, while Musk suggested Trump should be impeached, turning their bromance into an all-out brawl on social media.

The hostilities began when Trump criticized Tesla CEO Musk in the Oval Office. Within hours, the once-close relationship had disintegrated in full public view, as the world's most powerful man and its richest launched personal barbs at one another on Trump's Truth Social and Musk's X.

"The easiest way to save money in our Budget, Billions and Billions of Dollars, is to terminate Elon's Governmental Subsidies and Contracts," Trump posted on Truth Social.

Wall Street traders dumped shares of Musk's electric vehicle maker and Tesla closed down 14.3%, losing about $150 billion in market value. It was Tesla's largest single-day decline in value in its history.

Minutes after the closing bell, Musk replied, "Yes," to a post on X saying Trump should be impeached. Trump's Republicans hold majorities in both chambers of Congress and are highly unlikely to impeach him.

The trouble between the two started brewing days ago, when Musk denounced Trump's sweeping tax-cut and spending bill. The president initially held his tongue while Musk campaigned to torpedo the bill, saying it would add too much to the nation's $36.2 trillion in debt.

Trump broke his silence on Thursday, telling reporters in the Oval Office he was "very disappointed" in Musk.

"Look, Elon and I had a great relationship. I don't know if we will anymore," Trump said.

While Trump spoke, Musk responded with increasingly acerbic posts on X.

"Without me, Trump would have lost the election," wrote Musk, who spent nearly $300 million backing Trump and other Republicans in last year's election. "Such ingratitude."

In another post, Musk asserted that Trump's signature tariffs would push the U.S. into a recession later this year.

Besides Tesla, Musk's businesses include rocket company and government contractor SpaceX and its satellite unit Starlink.

Musk, whose space business plays a critical role in the U.S. government's space program, said that as a result of Trump's threats he would begin decommissioning SpaceX's Dragon spacecraft. Dragon is the only U.S. spacecraft currently capable of sending astronauts to the International Space Station.

Hours later, Musk appeared to reverse that move. Responding to a follower on X urging Musk and Trump to "cool off and take a step back for a couple of days," Musk wrote: "Good advice. Ok, we won't decommission Dragon."

In another possible sign of de-escalation on Thursday evening, Musk separately posted, "You're not wrong," in response to hedge fund manager Bill Ackman saying Trump and Musk should make peace.

PUGILISTIC PAIR

The feud was not entirely unexpected. Trump and Musk are both political pugilists with sizable egos and a penchant for using social media to punch back against their perceived enemies, and many observers had predicted an eventual falling out.

Even before Musk's departure from the administration last week, his influence had waned following a series of clashes with cabinet members over his cuts to their agencies.

For Trump, the fight was the first major rift he has had with a top adviser since taking office for a second time, after his first term was marked by numerous blow-ups.

Trump parted ways with multiple chiefs of staff, national security advisers and political strategists during his 2017-2021 White House tenure. A few, like Steve Bannon, remained in his good graces, while many others, like U.N. Ambassador John Bolton, became loud and vocal critics.

After serving as the biggest Republican donor in the 2024 campaign season, Musk became one of Trump's most visible advisers as head of the Department of Government Efficiency, which mounted a sweeping and controversial effort to downsize the federal workforce and slash spending.

Musk was frequently present at the White House and made multiple appearances on Capitol Hill, sometimes carrying his young son.

Only six days before Thursday's blowup, Trump and Musk held an appearance in the Oval Office where Trump praised Musk's government service and both men promised to continue working together.

A prolonged feud between Trump and Musk could make it more difficult for Republicans to keep control of Congress in next year's midterm elections. In addition to his campaign spending, Musk has a huge online following and helped connect Trump to parts of Silicon Valley and wealthy donors.

Musk had already said he planned to curtail his political spending in the future.

Soon after Trump's Oval Office comments on Thursday, Musk polled his 220 million followers on X: "Is it time to create a new political party in America that actually represents the 80% in the middle?"

'KILL THE BILL'

Musk targeted what Trump has named his "big, beautiful bill" this week, calling it a "disgusting abomination" that would deepen the federal deficit. His attacks amplified a rift within the Republican Party that could threaten the bill's prospects in the Senate.

Nonpartisan analysts say Trump's bill could add $2.4 trillion to $5 trillion to the nation's $36.2 trillion in debt.

Trump asserted that Musk's true objection was the bill's elimination of consumer tax credits for electric vehicles. The president also suggested that Musk was upset because he missed working for the White House.

"He's not the first," Trump said on Thursday. "People leave my administration... then at some point they miss it so badly, and some of them embrace it and some of them actually become hostile."

Musk wrote on X, "KILL the BILL," adding he was fine with Trump's planned cuts to EV credits as long as Republicans rid the bill of "mountain of disgusting pork" or wasteful spending.

He also pulled up past quotes from Trump decrying the level of federal spending, adding, "Where is this guy today?"

Musk came into government with brash plans to cut $2 trillion from the federal budget. He left last week having cut only about half of 1% of total spending while causing disruption across multiple agencies.

Musk's increasing focus on politics provoked widespread protests at Tesla sites in the U.S. and Europe, driving down sales while investors fretted that Musk's attention was too divided.