Employees who list endangered species, collect taxes and distribute aid to foreign countries are fearing for their livelihoods as they sift through rumors and wait to see whether their offices will be targeted for steep reductions.

The president said he’ll call for $54 billion in reductions to offset new spending for the Pentagon, and it should not come from veterans’ programs, law enforcement or entitlement programs, the biggest drivers of federal spending.

The math seems clear: To shrink government by that much, layoffs are inevitable, say federal officials, unions and budget experts. The White House already is eyeing deep cuts to the Environmental Protection Agency that could slash the agency’s career staff to 12,000 from 15,000, largely through buyout offers and layoffs. The State Department also could be in line for a big reduction, which some estimates peg at 37 percent.

“I don’t think there’s any way around it, this level of cuts will almost certainly lead to layoffs,” said Tony Reardon, president of the National Treasury Employees Union, which represents 150,000 federal workers across 31 departments. The union plans a rally on Capitol Hill on Thursday to highlight the damage to public services that could result from budget cuts. Meanwhile, Reardon said: “Our members are very, very concerned about job security.”