Treasury Secretary Janet Yellen has estimated that special measures can buy time for the US until at least June, at which point the government will no longer be able to pay its bills.
That is the scenario many analysts see as a true economic catastrophe.
In the event, some say authorities would have to do as much as they can to avoid default. That would mean finding ways to make interest payments while other obligations go unpaid, such as defence contractor payments; Social Security cheques, received by retirees across the country; and salaries of government employees, including the military.