WASHINGTON — The State Department will soon offer a $25,000 buyout to diplomats and staff members who quit or take early retirements by April, officials confirmed on Friday.

The decision is part of Secretary of State Rex W. Tillerson’s continuing effort to cut the ranks of diplomats and Civil Service officers despite bipartisan resistance in Congress. Mr. Tillerson’s goal is to reduce a department of nearly 25,000 full-time American employees by 8 percent, which amounts to 1,982 people.

To reach that number, he has already frozen hiring, reduced promotions, asked some senior employees to perform clerical duties that are normally relegated to lower-level staff members, refused to fill many ambassadorships and senior leadership jobs, and fired top diplomats from coveted posts while offering low-level assignments in their place. Those efforts have crippled morale worldwide.

Still, State Department accountants have told Mr. Tillerson that only about 1,341 people are expected to retire or quit by the end of September 2018, the date by which Mr. Tillerson has promised to complete the first round of cuts.