Visitors pass by the U.S. Capitol on Sept. 11, 2023, in Washington, D.C. (Photo: Chip Somodevilla/Getty Images)

(CNN) -- The possibility of a U.S. government shutdown is more likely with each passing day, as lawmakers have yet to reach an agreement to expand funding beyond the deadline at the end of the month.

Congress leaders from both parties are confident of passing a short-term funding extension to keep things going and avoid shutdown. But it's far from clear that such a plan will succeed amid deep divisions over spending between the two parties and political disagreements over issues such as aid to Ukraine.

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Here's what you need to know if the government shuts down and what's driving the current situation:

How could a government shutdown be triggered?

Government funding expires at the end of Saturday, September 30, when the clock strikes midnight and becomes October 1, which marks the start of the new fiscal year. (As an abbreviation, the deadline is commonly described as September 30 at midnight.)

If Congress does not pass a law to renew funding within that timeframe, the federal government will shut down at midnight. As this would occur over the weekend, the full effects of the shutdown would not be seen until the start of the workweek on Monday.


What might happen during a shutdown?

In the event of a shutdown, many government operations would stop, but some services deemed "essential" would continue.

Federal agencies have contingency plans that serve as a roadmap for what will continue and what will stop. For now, agencies still have time to review and update plans and it is not possible to predict exactly how government operations would be affected if a shutdown were to occur at the end of the month.

Government operations and services that continue during a shutdown are activities deemed necessary to protect public safety and national security or deemed critical for other reasons. Some examples of services that have continued during previous shutdowns are border protection, federal law enforcement, and air traffic control.

Federal employees whose work is deemed "non-essential" would be on leave, meaning they would not work and receive pay during the shutdown. Employees whose work is deemed "essential" would continue to work, but they would also not be paid during the shutdown.

Once the government shutdown ends, federal employees who were required to work and those who were furloughed will receive back pay.

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In the past, back pay for furloughed employees was not guaranteed, although Congress could and did act to ensure that those workers were compensated for lost wages after the shutdown ended. Now, however, back pay for furloughed workers is automatically guaranteed as a result of legislation led by Sen. Ben Cardin, D-Md., that was signed into law in 2019. Employees deemed "essential" and forced to work were already guaranteed back pay after a shutdown before the passage of that legislation.

And federal employees aren't the only ones who can feel the effects of a shutdown.

In previous closures, national parks have become one of the main focuses of attention. Although National Park Service sites across the country have been closed during previous government shutdowns, many remained open, but severely understaffed under the Trump administration, during a shutdown in 2019. Some park sites operated for weeks without visitor services provided by the Park Service, such as restrooms, trash collection, facilities or road maintenance.

"If you're a government worker, it's highly disruptive, whether you don't go to work or you do," said Maya MacGuineas, chairwoman of the Commission for a Responsible Federal Budget, a nonpartisan, nonprofit organization. "If you're someone who wants to use one of the services you can't access ... It's very disturbing. But for a lot of people... all the things they expect and are used to seeing from government keep happening and the inconvenience and the kind of waste of time and resources are not things they see and feel directly."

Why could the U.S. be headed for a government shutdown?

Right now, there is a deep divide between the House and Senate over efforts to reach consensus and pass spending legislation for the entire year, as hardline conservatives in the House push for deep spending cuts and controversial political additions than Democrats. As well as some Republicans, they have rejected them as too extreme.

With the funding deadline just around the corner, top lawmakers from both parties hope to pass a short-term funding extension, known on Capitol Hill as a continuing resolution, or CR. These short-term measures are often used as an interim solution to avoid a shutdown and buy more time to try to reach a broader funding agreement for the whole year.

It is unclear, however, whether there will be enough consensus to pass even a short-term funding bill in both chambers before the end of the month, as conservatives in the House of Representatives oppose the possibility of a stopgap bill and have threatened to vote against it. while demanding major political concessions that have no chance of being approved by the Senate.

The fight over aid to Ukraine could also take center stage and further complicate efforts to pass a bill in the short term.

Senate Democrats and Republicans strongly support additional aid to Ukraine, which could be included as part of a stopgap bill, but many House Republicans are reluctant to keep sending aid and don't want it attached to a short-term funding bill.

What has the White House said about the possible shutdown?

The White House has warned that a shutdown could jeopardize crucial federal programs.

In its warning, the White House estimated that 10,000 children would lose access to Head Start programs for low-income children across the country, as the Department of Health and Human Services would be barred from awarding grants during a shutdown, while air traffic controllers and Transportation Security Administration (TSA) officials would be prevented from providing grants during a shutdown. They would have to work without pay, threatening travel delays across the country. The shutdown would also delay food safety inspections by the Food and Drug Administration.

"These consequences are real and avoidable, but only if House Republicans stop playing politics with people's lives and addressing the ideological demands of their most extremist and far-right members," the White House said.

CNN's Marnie Hunter, Donald Judd and Piper Hudspeth Blackburn contributed to this report.

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