Fears of a US debt default are mounting as the deadline to lift the borrowing limit looms. Here's what Elon Musk, Paul Krugman and Jamie Dimon have warned.

• Fears of a US debt default are mounting as a deadline to raise the government's borrowing limit draws near.
• Treasury Secretary Janet Yellen has warned of worrying consequences if Congress doesn't make a decision soon.

Investors anxiety over the risk of a US debt default is mounting rapidly as a months-long political deadlock over the government's borrowing limit continues.

Lawmakers have been unable to break the impasse even though the Treasury is set to run out of money by June 1 if the $31.4 trillion ceiling isn't lifted by then. Republicans in Congress are willing to support an increase if spending cuts are imposed, while the White House insists on no such conditions.

The debate has garnered a range of insightful commentary from top voices, with some warning of a growing risk that the US could fail to repay the money it owes - with dire economic consequences.

Here's what six prominent figures have said about the ongoing political standoff over the debt ceiling.

Elon Musk, billionaire entrepreneur

Earlier this week, a Twitter user, Whole Mars Catalog, wrote that "defaulting on the national debt is a bad idea" in a recent tweet. Musk — the CEO of Tesla, SpaceX, and Twitter — replied with two worrying words: "Increasingly possible."

Paul Krugman, Nobel economist

"The possibility that the federal government will soon be unable to finance its normal operations has become very real," Krugman warned in a recent op-ed for the New York Times.

"If it happens, it will be because Republicans in the House are trying to use the debt ceiling to extort policy concessions they would have no chance of enacting through the normal legislative process," he said.

"You might ask how we're supposed to enforce a debt ceiling if the government can play games with the definition of debt. But the answer, of course, is that we shouldn't have a debt ceiling. The government should make decisions about taxing and spending, and consider the fiscal consequences, without creating an additional choke point that extremists can weaponize," he added.

Warren Buffett, Berkshire Hathaway CEO

"That is not how the US is going to behave, any more than they're going to let the debt ceiling cause the world to go into turmoil," Buffett said about the idea of the government letting depositors lose money in a bank failure, or refuse to allow more government borrowing, during his company's annual shareholder meeting.

Jamie Dimon, JPMorgan CEO

A default "is potentially catastrophic," Dimon told Bloomberg TV in an interview at the Wall Street bank's Global Markets Conference in Paris.

He said he doesn't expect the US to experience a debt default, but the deadline to reach a deal is soon approaching.

"The closer you get to it, you will have panic … Markets will get volatile, maybe the stock market will go down, the Treasury markets will have their own problems," said Dimon.

Janet Yellen, US Treasury Secretary

"It would also risk undermining US global economic leadership, and raise questions about our ability to defend our national security interests," Yellen said if the US were to default on its debt.

"Millions of Americans could lose their jobs, household incomes would be reduced. American businesses would see credit markets deteriorate, and millions of American families that receive government payments would likely be left without the resources that they were promised," she added.

"Almost certainly it would create global uncertainty about the value of the US dollar and US institutions and leadership, leading to volatility in currency and financial markets and commodity markets that are priced in dollars," she continued.

David Rosenberg, president of Rosenberg Research

"We have a possible debt default on our hands and a spreading bank crisis (sorry, Jamie, this doesn't look over), and the Fed is going to raise rates tomorrow. Focused on an inflation rate that is actually LOWER now than it was in July 2008. These guys are tone deaf," he recently tweeted.