The US is nearing its $41.1tn debt ceiling, with debt forecast to climb to about $64tn by 2036, according to the Congressional Budget Office.

But the situation is not yet critical, say economists. The US’s position as the world’s largest economy and the dollar being the world’s reserve currency gives the US a “much longer runway to fiscally misbehave” than other countries, El-Erian says.

“We’re getting to a point where it’s a flashing yellow light. It’s not a flashing red light,” he says.

Swanson says other countries have had similar, or higher debt levels.

While US national debt is 126% compared with the size of the economy, it’s lower than other G7 nations Japan and Italy.

But investor appetite in lending the US government money through buying bonds is “diminishing”, Swanson warns, creating a “vicious” cycle, requiring the government to offer ever higher returns to keep investors purchasing its debt.

And higher US borrowing costs inevitably spill over, raising other countries’ borrowing costs too. “What happens in the US never stays in the US,” says El-Erian.

Charlie Bean, emeritus economics professor at the London School of Economics, says that if the US debt to economy ratio hits a certain point it could start a fire sale of US bonds and lead to financial market turmoil.

“There probably is a point, but unfortunately we don’t know where it is,” he says.

“It’s not as if there’s a fixed number that we could say, you know, ‘if it gets to 150 percent, you know, disaster will happen, but we’re OK if we stay at 145’.”