U.S. President Donald Trump on Tuesday threatened to cut off the billions of dollars in subsidies that Elon Musk's companies receive from the federal government, in an escalation of the war of words between the president and the world's richest man, one-time allies who have since fallen out, Reuters reported.

The feud reignited on Monday when Musk, who spent hundreds of millions on Trump's re-election, renewed his criticism of Trump's tax-cut and spending bill, which would eliminate subsidies for electric vehicle purchases that have benefited Tesla, the leading U.S. EV maker. That bill passed the Senate by a narrow margin midday Tuesday.

"He's upset that he's losing his EV mandate and … he's very upset about things but he can lose a lot more than that," Trump told reporters at the White House on Tuesday.

Though Musk has often said government subsidies should be eliminated, Tesla has historically benefited from billions of dollars in tax credits and other policy benefits because of its business in clean transportation and renewable energy. The Trump administration has control over many of those programs, some of which are targeted in the tax bill, including a $7,500 consumer tax credit that has made buying or leasing EVs more attractive for consumers, according to Reuters.