Washington(CNN) President Donald Trump told lawmakers on Thursday he wants to scrap a pay raise for civilian federal workers, saying the nation's budget couldn't support it.

In a letter to House and Senate leaders, Trump described the pay increase as "inappropriate."

"We must maintain efforts to put our Nation on a fiscally sustainable course, and Federal agency budgets cannot sustain such increases," the President wrote.

An across-the-board 2.1% pay increase for federal workers was slated to take effect in January. In addition, a yearly adjustment of paychecks based on the region of the country where a worker is posted -- the "locality pay increase" -- was due to take effect.

Trump said both increases should no longer happen.

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"I have determined that for 2019, both across the board pay increases and locality pay increases will be set at zero," he wrote.

Congress has an opportunity to effectively overrule the President's edict if lawmakers pass a spending bill that includes a federal pay raise. The Senate passed a bill this summer that included a 1.9% raise for federal workers. The House's version did not address federal pay. Senate and House negotiators will negotiate a final measure in the coming weeks.

Trump's 2019 budget proposal, released earlier this year, included a pay freeze for civilian federal workers. It's not clear if Trump would approve a budget that includes the pay increase; the White House has not issued a formal veto threat of the Senate's bill.

In his letter, Trump stressed a pay freeze would not affect the federal government's ability to attract qualified workers, and wrote the government would focus on "recruiting, retaining and rewarding high-performing Federal employees and those with critical skill sets."

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The implications of Trump's decision on the locality pay increase were not immediately clear. Workers based in more expensive parts of the country are paid higher salaries to compensate for the higher cost of living.

In his letter, Trump wrote the locality increase in 2019 would average 25.70% and cost the federal government $25 billion. But he did not say whether the locality adjustments already in place would remain in effect and the White House did not immediately clarify.

Pay for military personnel will not be affected by Trump's decree; instead, US troops are due a 2.6% pay increase next year. Trump frequently trumpets the military pay raise while listing his administration's accomplishments. The raise came as part of a massive $716 billion defense spending bill that Trump signed earlier this month.

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That measure, along with a new two-year federal budget and tax cuts heralded by Republicans, have led to accusations Trump is ignoring the federal deficit, despite promising he would address it as president. The tax plan alone is expected to increase the deficit by $1.4 trillion over 10 years, according to a government estimate.

In ordering the raises canceled, Trump cited his statutory authority to adjust pay because of "national emergency or serious economic conditions affecting the general welfare." Yet the President frequently touts a growing US economy, including a strong growth rate for the gross domestic product and low unemployment

"These numbers are very, very sustainable -- this isn't a one-time shot," he said last month after figures showed the US economy grew at a 4.1% annual rate in the second quarter of the year.

The pay raise matter was the latest in a string of moves that reflect an attempt to rein in spending on federal employees. Trump signed executive orders in May that made it easier to fire federal employees and placed limits on public-sector unions. A judge struck down most of those provisions last week.

Reaction on Thursday from Democrats was swift, particularly those from states adjacent to Washington, where large numbers of federal workers reside.

"Zero. This seems to be how much respect President Trump has for federal workers," wrote Sen. Ben Cardin, D-Maryland, in a statement. "It is outrageous and hypocritical that after spending billions of taxpayer dollars on unnecessary tax cuts for the wealthy and big corporations -- and as the President boasts about the 'great' state of the American economy, that suddenly the White House finds that there is zero money left to pay a minimal cost-of-living adjustment to the patriotic, dedicated public servants."

Sen. Mark Warner, D-Virginia, wrote: "Let's be clear: The President's decision to cancel any pay increase for federal employees is not motivated by a sudden onset of fiscal responsibility. Today's announcement has nothing to do with making government more cost-efficient -- it's just the latest attack in the Trump administration's war on federal employees."

While the Washington area contains the largest concentration of federal workers, only 1-in-6 civilian employees of the government live in the region.

The state with the largest number of federal workers is California, followed by Virginia, the District of Columbia and Texas. States Trump won in 2016 -- including Florida, Pennsylvania and Ohio -- also rank high on the list of states where federal employees work.