The threat of a US government shutdown has become common in a divided Washington. The clock is again ticking for Congress to pass a short-term government funding measure to stave off a shutdown of large portions of the federal government.
Speaker Mike Johnson, who leads the majority Republican Party in the House of Representatives, is struggling to gain support for a continuing resolution to keep agencies open over the Christmas holiday, as president-elect Donald Trump and billionaire Elon Musk air fierce opposition.
News reports say Mr Trump supports Mr Johnson's inclusion of aid for farmers and relief for natural disaster survivors, but he led a tirade against Republicans to "get smart and tough" in stripping Democratic priorities out of the bill.
Mr Trump especially wants to "terminate or substantially extend" the debt ceiling, which is a difficult challenge for Mr Johnson to handle, along with Republicans who have long voted against debt limit increases.
What happens if the US government shuts down?
Should Congress fail to fund the government, federal agencies will be required to halt all non-essential operations. Essential functions will continue. This will affect a range of activities, from national parks to passport applications.
Some federal employees will also be told to not report to work. More than 800,000 federal employees were furloughed during the 2013 shutdown, as explained by the Office of Management and Budget. The furloughs would lead to prolonged waiting times on passport applications and small business loans.
Most federal buildings and attractions – such as the Smithsonian museums in Washington – would be closed. National parks would be open, but travelling to one would come with an increased risk as the National Park Service would not be able to maintain visitor centres, rest rooms and roads.
The White House said a shutdown would "hurt hardworking Americans and create instability across the country".
President Joe Biden's administration said that the incoming Trump government is threatening not to support "communities recovering from disasters, farmers, ranchers, and community health centres".
"Triggering a damaging government shutdown would hurt families who are gathering to meet with their loved ones and endanger the basic services Americans from veterans to Social Security recipients rely on," the White House said.
How would a shutdown affect the economy?
A shutdown could also affect the US economy and the nation's credit rating, according to Moody's review of past similar situations.
“A shutdown would be credit-negative for the US sovereign,” credit ratings agency Moody's said to clients.
A government-wide shutdown would reduce economic growth by about 0.15 percentage points for each week it lasts, Goldman Sachs says.
How many times has the government shut down?
The federal government has shut down 21 times over the past five decades. The most recent shutdown was also the longest.
From December 2018 to January 2019, former president Donald Trump forced a government shutdown to receive funding for the US-Mexico border wall. That ended after 35 days without any such funding.
It was one of three shutdowns to have happened during Mr Trump's term. The first lasted for three days, and the second only for a few hours.