A partial government shutdown looks probable as President Donald Trump digs in his heels on his demand to fund a border wall.

Congress has until midnight Friday to either pass spending bills for seven federal agencies, or approve a stopgap spending measure that would push off a potential shutdown. If those efforts fail, the closure could affect hundreds of thousands of Americans’ jobs through the holidays.

Trump wants $5 billion in funding to build a wall along the U.S.-Mexico border, and has said he would be “proud” to shut the government down if Congress doesn’t accede to his demand.

The Office of Management and Budget started notifying federal agencies Thursday that they should prepare for a shutdown. Yet since lawmakers have already funded large portions of the government through the 2019 fiscal year, the current crisis would only shut down parts of the government. The unfunded agencies make up about a quarter of the government.

This is what could happen if there is a shutdown this weekend:

More than 420,000 federal employees across numerous agencies will continue to work even if the government shuts down. They just won’t get paid for it immediately.

Democrats on the Senate Appropriations Committee say that number will include more than 41,000 federal law enforcement and correctional officers from the FBI, the Drug Enforcement Agency, the Bureau of Alcohol, Tobacco, Firearms and Explosives, and thousands of other law enforcement and correctional officers.

The vast majority of Department of Homeland Security employees will also work without a regular paycheck. The nearly 90 percent of workers in the agency affected by a shutdown would include 53,000 Transportation Security Administration employees, as well as 42,000 Coast Guard employees.

As many as 54,000 employees from Customs and Border Protection — the agents who are currently working to secure the southern U.S. border — are also projected to work without paychecks. By forcing a shutdown over border security, Trump would cause the agents he often lauds for their efforts to stop illegal immigration to temporarily go without compensation.

Up to 5,000 Forest Service firefighters and 3,600 National Weather Service forecasters will also keep working without paychecks, according to Senate Democrats.

The special counsel’s office, which is investigating potential criminal connections between the Trump campaign and the Kremlin, will continue operating.

Another 380,000 federal workers or more would be placed on temporary leave without receiving pay in the event of a government shutdown, according the Democrats.

Furloughs would affect vast swathes of Department of Commerce and NASA staff. About 41,000 people, or 86 percent, would be furloughed from the Commerce Department, along with a staggering 96 percent of NASA employees.

Four-fifths of the Forest and National Park Services, totaling more than 44,000 employees, would be sidelined, as would approximately 52,000 staff from the IRS, and about 7,100 Housing and Urban Development workers — 95 percent of the total.

Thirty percent of Transportation Department employees, equaling about 18,300, would be furloughed, as well.

All of that lost work could cost taxpayers huge amounts of money. An Office of Management and Budget review of a 2013 government shutdown during the Obama administration concluded that the cost of “the lost productivity of furloughed workers” alone was $2 billion. The cost may not go that high this time with five agencies still running.

That shutdown was one of the longest in U.S. history. A failure to fund the government by midnight Friday would likely create a closure that lasts into the new year, when Democrats take majority control of the House.

Trump himself said in a tweet Friday morning that “if the Dems vote no, there will be a shutdown that will last for a very long time.”