WASHINGTON (AP) — The government's chief human resources agency issued a new rule on Thursday making it harder to fire thousands of federal employees, hoping to head off former President Donald Trump's promises to radically remake the workforce along ideological lines if he wins back the White House in November.

The Office of Personnel Management regulations will bar career civil servants from being reclassified as political appointees or as other at-will workers, who are more easily dismissed from their jobs. It comes in response to Schedule F, an executive order Trump issued in 2020 that sought to allow for reclassifying tens of thousands of the 2.2 million federal employees and thus reduce their job security protections.

President Joe Biden nullified Schedule F upon taking office. But if Trump, a Republican, were to revive it during a second administration, he could dramatically increase the around 4,000 federal employees who are considered political appointees and typically change with each new president.

In a statement issued Thursday, Biden, a Democrat, called the rule a "step toward combatting corruption and partisan interference to ensure civil servants are able to focus on the most important task at hand: delivering for the American people.'

The potential effects of the change are wide-reaching since how many federal employees might have been affected by Schedule F is unclear. The National Treasury Employee Union used freedom of information requests to obtain documents suggesting that workers like office managers and specialists in human resources and cybersecurity might have been among those subject to reclassification.

The new rule moves to counter a future Schedule F order by spelling out procedural requirements for reclassifying federal employees and clarifying that civil service protections accrued by employees can't be taken away, regardless of job type. It also makes clear that policymaking classifications apply to noncareer, political appointments.

"It will now be much harder for any president to arbitrarily remove the nonpartisan professionals who staff our federal agencies just to make room for hand-picked partisan loyalists," National Treasury Employees Union President Doreen Greenwald said in a statement.

Good government groups and liberal think tanks and activists have cheered the rule. They viewed cementing federal worker protections as a top priority given that replacing existing government employees with new, more conservative alternatives is a key piece of the conservative Heritage Foundation's nearly 1,000-page playbook known as Project 2025.

That plan calls for vetting and potentially firing scores of federal workers and recruiting conservative replacements to wipe out what leading Republicans have long decried as the "deep state" governmental bureaucracy.

Skye Perryman, president and CEO of Democracy Forward, which has led a coalition of nearly 30 advocacy organizations supporting the rule, called it "extraordinarily strong" and said it can effectively counter the "highly resourced, anti-democratic groups" behind Project 2025.

"This is not a wonky issue, even though it may be billed that way at times," Perryman said. "This is really foundational to how we can ensure that the government delivers for people and, for us, that's what a democracy is about."

The final rule, which runs to 237 pages, is being published in the federal registry and set to formally take effect next month. The Office of Personnel Management first proposed the changes last November, then reviewed and responded to 4,000-plus public comments on them. Officials at some top conservative organizations were among those opposing the new rule, but around two-thirds of the comments were supportive.

If Trump wins another term, his administration could direct the Office of Personnel Management to draft new rules. But the process takes months and requires detailed explanation on why new regulations would be improvements — potentially allowing for legal challenges to be brought by opponents.

Rob Shriver, deputy director of the Office of Personnel Management, said the new rule ensures that federal employee protections "cannot be erased by a technical, HR process" which he said "Schedule F sought to do."

"This rule is about making sure the American public can continue to count on federal workers to apply their skills and expertise in carrying out their jobs, no matter their personal political beliefs," Shriver said on a call with reporters.

He noted that 85% of federal workers are based outside the Washington area and are "our friends, neighbors and family members," who are "dedicated to serving the American people, not political agendas."