President Trump on Thursday will unveil a budget plan that calls for a sharp increase in military spending and stark cuts across much of the rest of the government including the elimination of dozens of long-standing federal programs that assist the poor, fund scientific research and aid America’s allies abroad.

Trump’s first budget proposal, which he named “America First: A Budget Blueprint to Make America Great Again,” would increase defense spending by $54 billion and then offset that by stripping money from more than 18 other agencies. Some would be hit particularly hard, with reductions of more than 20 percent at the Agriculture, Labor and State departments and of more than 30 percent at the Environmental Protection Agency.

It would also propose eliminating future federal support for the National Endowment for the Arts, the National Endowment for the Humanities and the Corporation for Public Broadcasting. Within EPA alone, 50 programs and 3,200 positions would be eliminated.

The cuts could represent the widest swath of reductions in federal programs since the drawdown after World War II, probably leading to a sizable cutback in the federal non-military workforce, something White House officials said was one of their goals.

“You can’t drain the swamp and leave all the people in it,” White House Office of Management and Budget Director Mick Mulvaney told reporters.

Many of Trump’s budget proposals are likely to run into stiff resistance from lawmakers on Capitol Hill, even from Republicans, whose support is crucial because they must vote to authorize government appropriations. Republicans have objected, for example, to the large cuts in foreign aid and diplomacy that Trump has foreshadowed, and his budget whacks foreign aid programs run by the Education, State and Treasury departments, among others.

“The administration’s budget isn’t going to be the budget,” said Sen. Marco Rubio (R-Fla.). “We do the budget here. The administration makes recommendations, but Congress does budgets.”

Trump’s budget would not take effect until the new fiscal year on Oct. 1, but the president must still reach a separate agreement with Congress by the end of April, when a temporary funding bill expires. If they can’t reach an agreement, and if Trump’s new budget plan widens fault lines, then the chances would increase for a partial government shutdown starting on April 29.

The president and Congress must also raise the debt ceiling, which has become a politically fraught ritual. Although the ceiling was extended until March 15, budget experts say the government should be able to continue borrowing money by suspending or stretching out payments through August or September.

White House budget proposals are often changed by lawmakers, but they serve as a marker for how the president plans to govern and as an opening bid on budget talks. Mulvaney said the White House was open to negotiation, but he was unapologetic about the size and scope of the reductions.

“This budget represents a president who is beholden to nobody but the voters,” Mulvaney said. “He is following through on his promises. We did not consult with special interests on how to write this budget. We did not consult with lobbyists on how to write this budget. The president’s team wrote this budget and that’s what you’ll see in the numbers.”

The 53-page budget plan offers the clearest snapshot yet of Trump’s priorities. Yet it is also far shorter and vaguer than White House budget plans normally are. One of the missing details is precisely where and how many jobs would be eliminated across the federal government.

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[Read President Trump’s first budget proposal]

Parts of the budget proposal also appear to contradict Trump’s agenda. Trump has said he wants to eliminate all disease, but the budget chops funding for the National Institutes of Health by $5.8 billion, or close to 20 percent. He has said he wants to create a $1 trillion infrastructure program, but the proposal would eliminate a Transportation Department program that funds nearly $500 million in road projects. It does not include new funding amounts or a tax mechanism for Trump’s infrastructure program, postponing those decisions.

And the Trump administration proposed to eliminate a number of other programs, particularly those that serve low-income Americans and minorities, because it questioned their effectiveness. This included the Low-Income Home Energy Assistance Program, which disburses more than $3 billion annually to help heat homes in the winter. It also proposed abolishing the Community Development Block Grant program, which provides roughly $3 billion for targeted projects related to affordable housing, community development and homelessness programs, among other things.

The budget was stuffed with other cuts and reductions. It calls for privatizing the Federal Aviation Administration’s air traffic control function, cutting all funding for long-distance Amtrak train services and eliminating EPA funding for the restoration of Chesapeake Bay. Job training programs would also be cut, pushing more responsibility for this onto the states and employers.

Many Republicans have criticized these programs in the past as wasteful and ineffective, but supporters have said the programs are vital for communities in need.

The proposed budget extensively targets Obama programs and investments focused on climate change, seeking to eliminate payments to the United Nations’ Green Climate Fund — one key component of the U.S. commitment to the Paris climate agreement — and to slash research funding for climate, ocean and earth science programs at agencies such as NASA and the National Oceanic and Atmospheric Administration. At the same time, clean-energy research, heavily privileged by the Obama administration, would suffer greatly under the budget with the elimination of the ­ARPA-E program (Advanced Research Projects Agency-Energy) at the Energy Department and an unspecified cut to the agency’s Office of Energy Efficiency and Renewable Energy.

“I think one of the reasons they’re proposing them [big spending cuts] is that they know they won’t ever get through Congress,” said Sen. Patrick J. Leahy (D-Vt.). “They know they’d be a disaster for their own party if they did. It makes for a great talking point. It actually fits on a tweet.”

There were several areas in which Trump proposed increasing spending. He proposed, for example, $168 million for charter school programs and $250 million for a new private-school choice program, which would probably provide tuition assistance for families who opt to send their children to private schools.

The biggest increase in spending would be directed at the Pentagon, but the budget plan does not make clear where the new $54 billion would go. The budget plan would boost funding for the Army, Navy, Marine Corps and Air Force. It would, among other things, acquire new F-35 Joint Strike Fighters and rebuild what it says are depleted munitions inventories. But it stops short of saying how these new funds would support new tactics to combat the Islamic State.

The bump in defense spending was a marked contrast to the cuts Trump proposed in diplomatic and international programs. He proposed cutting combined spending for the State Department and the U.S. Agency for International Development by $10.1 billion, or nearly 29 percent. It would cut an unspecified amount of funding from U.N. peacekeeping efforts. It would also cut spending for Treasury International Programs, foreign assistance programs that have been supported by Republican and Democratic administrations, by $803 million, or 35 percent.

Trump directed funding to meet several of his campaign pledges as well.

He proposed new money to hire border security agents and immigration judges.

And he requested $1.7 billion in new funding this year and an additional $2.6 billion in new funding in 2018 to begin construction of a wall along the border with Mexico. Trump proposed creating this wall during his campaign and had said Mexico would pay for it. A number of congressional Republicans appear to be cooling on the idea.

The federal government is expected to spend more than $4 trillion in the fiscal year that begins in October, and Trump’s budget proposal would deal with slightly more than 25 percent of this funding. The government is expected to spend $487 billion more than it brings in through revenue during the next fiscal year, and to avoid widening the deficit, Trump proposed steep cuts across the budget to compensate for the new defense spending.

Trump will propose a more comprehensive budget plan in May, which could include changes to programs such as Medicaid and also offer economic forecasts. But that proposal will come after the deadline for reaching an agreement to avoid a partial shutdown. So Thursday’s budget proposal from Trump will factor squarely into those negotiations.

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Kelsey Snell and Philip Rucker contributed to this report.