With Democrats and President Trump seemingly at an impasse over a spending bill – particularly in regards to funding for border security – the government partially shuttered at midnight, just in time for the Christmas break. And Trump has warned that a closure could drag on “for a very long time.”

He had urged Senate Republicans to use the so-called “nuclear option” to pass a spending bill that includes enough funding for a border wall. The House scrambled to put together a package late Thursday that included the $5.7 billion the president wants, but was unable to agree on a deal to fund the government by Friday.

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Senate Majority Leader Mitch McConnell has often rebuffed calls to use the nuclear option, which would change Senate procedure to require only a simple majority to approve the spending bill. The Senate plans to reconvene at noon Saturday to continue talks.

About one-quarter of the government will be affected in a shutdown.

According to a precedent set during the Reagan administration, federal workers can be exempt from furloughs if their jobs are related to national security or if they perform essential activities that “protect life and property.”

Read on for a look at which agencies are closed during a partial shutdown and who still is expected at work.

What departments will close?

Nine of the 15 Cabinet-level departments will shutter, along with dozens of agencies. Those departments are: Agriculture, Commerce, Homeland Security, Housing and Urban Development, Interior, Justice, State, Transportation and Treasury.

Essential personnel would still be required to work but without pay. Nearly 90 percent of the Homeland Security staff is deemed essential.

WHAT IS THE ‘NUCLEAR OPTION,’ THE STEP TRUMP WANTS THE SENATE TO TAKE?

With the Interior Department impacted, many national parks and forests will close.

Who will have to work without pay?

More than 420,000 people – including law enforcement and Homeland Security workers – will have to work with their pay withheld, according to Senate Democrats.

About 53,000 TSA employees, 54,000 Customs and Border Protection agents and 42,000 Coast Guard workers would be required to work without pay.

TRUMP BACKS CALL TO NUKE FILIBUSTER IN DRIVE TO PASS BORDER WALL FUNDING AS SHUTDOWN LOOMS

Additionally, about 5,000 Forest Service firefighters would need to work, according to Senate Democrats.

Who will be furloughed?

More than 380,000 people will be furloughed in the shutdown – meaning they will experience a temporary leave from their work.

WOULD A GOVERNMENT SHUTDOWN IMPACT HOLIDAY TRAVEL, MAIL?

This will include most of NASA, Department of Housing and Urban Development, Commerce Department and National Park Service workers. Additionally, about 52,000 IRS workers would be furloughed.

Would this affect the mail or holiday travel?

The U.S. Postal Service (USPS) will remain open as usual during a partial government shutdown because it is “an independent entity that is funded through the sale of our products and services, and not by tax dollars,” a spokesman told Fox News.

TSA agents, air traffic controllers and border security agents also will be required to work through a shutdown – albeit they might not get a paycheck right away.

Amtrak, a government-owned corporation, also will continue with normal operations during a short-term shutdown, a spokeswoman confirmed to Fox News.

The Associated Press contributed to this report.