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.

The political stalemate over increasing it is deepening. If it is not resolved, there is a looming risk that the US government could default on its debt.

That 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.