Without an agreement on a budget deal between Republican and Democratic negotiators, a partial shutdown of the US government would start on Saturday.
The full impact is not likely to be felt until Monday morning when most of the 4.4 million federal employees are due to go to work.
The game of brinksmanship between the Republicans and the Democrats is over how much to cut government spending and what exactly to cut.
The White House says with its plan the budget deficit would be reduced over the next four years from the current 10.9 percent to 3.6 percent. The Republicans say that is not enough.
Based on previous shutdowns, around 800,000 federal workers considered to be nonessential would be told to stay home.
Every branch of government would be disrupted, apart from vital services such as national defence, emergency medical care and air traffic control.
Federal employees have been told that they may not voluntarily work during a shutdown and they will get their pay only if the US Congress approves such funding after a shutdown ends.