WASHINGTON —

After days of warnings, the White House has initiated mass layoffs of federal employees during the government shutdown, an unusual step that has already prompted a lawsuit from labor unions.

The American Federation of Government Employees argues the firings represent an "illegal, unprecedented abuse of power."

In a court filing , the White House Office of Management and Budget said more than 4,000 employees would be fired. The document includes a list of estimated layoffs by agency, but emphasizes that the situation is "fluid" and the numbers are "subject to change."

Department of the Treasury: 1,446

Health and Human Services: 1,100-1,200

Department of Education: 466

Department of Housing and Urban Development: 442

Department of Commerce: 315

Department of Energy: 1

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