The White House's Office of Management and Budget is planning for a lapse in funding as of Thursday evening in preparation for a possible shutdown, an OMB official told CNN.
The official said OMB had contacted government agencies seven days ago, telling them to be prepared for the possibility of government shutdown, and on Thursday OMB emailed the agencies, advising them to get their plans together and to update staff on who will be affected and what the plan would be.
Just hours ahead of the midnight deadline to keep the government open, Republican Sen. Rand Paul of Kentucky held up a key vote on a spending agreement backed by leaders of both parties in the Senate as well as President Donald Trump.
The official said it is up to individual agencies how they would handle a shutdown, but even those affected by a potential lapse in appropriations would be able to come into work for up to four hours to conduct an orderly shutdown.
The official added that all of the agencies' shutdown plans are listed on OMB's website, and that just as during January's brief government stoppage, many workers in safety and security are considered exempt from a shutdown.
A senior administration official said the White House instructed agencies Thursday evening to begin shutdown preparations in the event Congress fails to pass a funding agreement before the midnight deadline.
The full impact of any shutdown would depend on its length. The current run of funding is due to end at midnight, and if Paul's block passes that point or appropriations otherwise lapse, the government would be in a state of shutdown. But if an agreement is reached shortly after the deadline, most operations would not be affected.
If a shutdown continues into the morning -- as most agencies begin their workdays and government operations not authorized to continue during a shutdown would normally begin -- workers across the government would begin to go on furlough until appropriations resume, although the OMB official noted that those affected would be able to work for four hours to smooth the process.
Asked about the possibility of a shutdown on Wednesday, Defense Secretary James Mattis said it would be "very damaging." He noted that during a shutdown the Department of Defense sends home "all non-uniformed personnel except those in a few critical areas" and that while military operations would continue, training would be delayed.
"It just paralyzes everything that we do if we go into that," Mattis said.
"The impact just ripples through the force," he said.
As contingency plans collected on the OMB's website show, agencies across the government have plans in place for shutdowns, many of which were updated ahead of the shutdown last month and some as recently as Thursday.
In addition to security operations, many other services are deemed essential -- the mail still goes out, Social Security benefits come in -- and continue without funding, though thousands of other federal workers across the country would go on furlough and offices close.