A unique rule in America’s fiscal system means that the world’s largest economy is about to run out of money.

US lawmakers have been arguing over whether to raise or suspend the so-called “debt ceiling”, which determines how much money the US government can borrow.

Treasury Secretary Janet Yellen has warned that if the continuing impasse between Republicans and Democrats is not broken, the administration will not have enough cash to pay its debts as early as June 1.

Meanwhile, Fitch Ratings has threatened the US economy with a downgrade of its AAA status, saying that ‘risks have risen’ that the debt ceiling will not be resolved.

Fitch warned: “We believe risks have risen that the debt limit will not be raised or suspended before the x-date [when the government expects to run out of money] and consequently that the government could begin to miss payments on some of its obligations.”

The deepening political stalemate and the looming risk that the US government could default on its debt has prompted some Democrats to call on Joe Biden to sidestep the Republicans and avoid a default by invoking the 14th Amendment. But experts say that would be fraught with legal risk.