The White House and the Congress have until Friday to reach agreement on an elusive federal spending-cut bill -- or face a partial shutdown of the U.S. government beginning the next day.
Relatively few federal employees work on weekends, so the impact of a shutdown likely won't be felt much until Monday morning when millions of them are set to report to work.
With federal agencies under orders to get ready for a shutdown, it is unclear how matters will unfold. But some tax refunds could get delayed, calls to federal hotlines may go unanswered and national parks will close. Social Security checks, however, are to go out on time.
Most of the 4.4 million federal workforce, including members of the U.S. military, will go to work because their jobs are deemed essential.
It's been 15 years since the last government shutdown over spending disagreements. Here are some facts about what could happen:
* Based on previous shutdowns, several hundred thousand federal workers could be idled as nonessential, disrupting all but vital U.S. services such as national defense, emergency medical care and air traffic control. In addition, some employees of federal contractors may also be furloughed.
* Unlike the last two shutdowns, both of which occurred in the 1990s, this one would take place during tax preparation and filing season. That could mean delayed tax refunds to an untold number of Americans, congressional aides say.
* The last shutdown closed much of the federal government from December 16, 1995, to January 6, 1996. National parks and museums were closed, an estimated 200,000 applications for U.S. passports went unprocessed and work on more than 3,500 bankruptcy cases was suspended.
* Also during the last shutdown, new patients were not accepted into clinical research at the National Institutes of Health, hotline calls to NIH about diseases were not answered, and toxic waste cleanup work at 609 sites stopped.
* A shutdown may be felt on a number of fronts, including delays in approving import and export licenses and new benefits for military veterans, congressional aides say. Processing new Social Security applications may also be delayed, but checks for retirees are expected to go out on time.
* Essential personnel in the last shutdown -- employees who remained on the job -- included members of the U.S. military, federal criminal investigators, those involved in federal disaster assistance and workers vital to keeping crucial elements of the U.S. money and banking system up and running.
* Since 1980, all federal agencies have been required to have updated plans for potential shutdowns that include who would be furloughed and who would be kept on the job.
* Polls show the public would hold Democrats and Republicans equally to blame for any shutdown. Both parties insist that they want to keep the government open.
(Source: the Office of Management and Budget, the Congressional Research Service, congressional aides)
(Reporting by Thomas Ferraro in Washington; Editing by Paul Simao and Doina Chiacu)