The message comes from Russ Vought, head of the White House's powerful management and budget agency (OMB), who writes that "the cuts have begun" on X.
Figures on how many are forced to go have not been made public, but have been promised by President Donald Trump in the future.
Closures are not entirely unusual in the USA. But usually, government employees are only laid off, and get their jobs back when a temporary budget has been approved and the government apparatus is up and running again.
Friday's message is considered an aggressive tactic from the White House to force Democratic members of the Senate to vote through the budget.
The Republicans have a majority in the Senate, with 53 out of a total of 100 members. But to get a budget through, 60 votes are required.
The Democrats have tried to call the government's hand, partly because the White House – until today – had not made its threats of layoffs a reality.
