Federal employees came a step closer to receiving a 1.6 percent raise in January with a letter Wednesday from President Obama to Congress setting that amount by default if no figure is enacted into law by the end of the year.

Congress so far has made no move toward legislating a raise, with both the House and Senate remaining silent in the annual spending bill that typically specifies one. Under the complex federal pay law, such inaction paves the way for a raise to be paid by default.

The letter sets an “alternative” to the much larger increase that otherwise would take effect under that law. It did not specify how large that raise would be, but a similar letter issued last year in the same situation said the default raise otherwise would be nearly 29 percent.

The 1.6 figure is not definitive because any law enacted before year’s end setting a different number would make the letter moot. However, Congress so far this year has been continuing a practice of the past three years when raises of 1, 1 and 1.3 percent were allowed to take effect by default for 2014-2016.

In each case, a similar letter from the White House also repeated the figure it sought in its early-year budget proposal.

Under the letter, a 1 percent increase would be paid across the board and the money for the other 0.6 percentage points would be divided up as locality pay, resulting in raises ranging in various metro areas from slightly above to slightly below 1.6 percent. Exact figures would be set in the fall after a study group receives data from the Labor Department on local pay differences between federal and nonfederal jobs.

“These decisions will not materially affect our ability to attract and retain a well-qualified Federal workforce,” the letter says.

The order technically applies only to employees in the General Schedule, the pay system for white-collar employees below the senior ranks. However, spending bills crafted so far would continue a long-standing practice of paying blue-collar employees the same localized amounts, even though those employees are under a separate pay system.

Those bills also would prevent a raise for political appointees or for members of Congress.

The General Schedule raise also does not apply to career senior executives and other senior-level employees, who are paid under separate systems in which raises are linked to performance evaluations. A general raise lifts the pay caps applying to them, however.

While a 1.6 percent raise would be the largest since 2010 — federal salary rates were frozen in 2011-2013 — federal employee organizations, with the backing of some Democratic members of Congress, have been seeking a 5.3 percent increase for 2017.

National Treasury Employees Union president Tony Reardon said in a statement that the 1.6 percent amount “is far too low given the last few years’ erosion in federal pay — from the recent three-year pay freeze to the last three years of meager raises. We continue to highlight the impact on federal workers of low pay increases and the impact on federal agencies’ ability to recruit and retain the skilled workforce our nation needs.”

“A 1.6 percent pay raise does nothing to make up for years of pay freezes,” American Federation of Government Employees president J. David Cox Sr. said in a statement, and minuscule increases “that have left federal employees worse off today than they were at the start of the decade.”

In addition to the general increases, a federal employee’s pay can rise for other reasons, including a promotion and advancing up a pay ladder, for those under pay systems with that structure.

Under a separate letter, military personnel also would receive a 1.6 percent raise if no figure is legislated for them.

The raise order has no effect on benefits for federal retirees. They receive cost-of-living adjustments (COLAs) linked to an inflation index under the same formula used to set Social Security COLAs.

With two months remaining in the pertinent counting period, that adjustment stands at just 0.2 percent.