The Trump administration could cut nearly 50 percent of the State Department’s funding next fiscal year, according to an internal memo laying out a downsizing plan being given serious consideration by department leaders, said two U.S. officials. The plan was drawn up as the White House pressures agencies to make significant budget cuts.

The memo, a copy of which was obtained by The New York Times, proposes eliminating almost all funding for international organizations like the United Nations and NATO, ending the budget for supporting international peacekeeping operations and curtailing all of the department’s educational and cultural exchanges, like the Fulbright Program.

It also proposes cutting funding for humanitarian assistance and global health programs by more than 50 percent despite Secretary of State Marco Rubio’s pledges that lifesaving assistance would be preserved.

It was not clear if Mr. Rubio had endorsed the cuts outlined in the memo, which was dated April 10. Pete Marocco, who oversaw the gutting of government foreign aid programs before abruptly leaving the department, and Douglas Pitkin, who is in charge of the department’s budget planning, prepared the document. It was also not clear how seriously the proposed cuts would be entertained in Congress, which appropriates federal Dollars.

But, according to a U.S. official familiar with the department’s review, it is likely that the White House will send Congress a budget proposal this spring that is substantially similar to what the memo outlines in an effort to press lawmakers to formalize downsizing efforts that are already underway.

Agencies are facing a deadline this week to submit detailed reorganization plans to the White House explaining what cuts they will make to help further shrink the federal government. While many departments have already announced or begun carrying out their planned cuts, the State Department has yet to publicly detail complete plans for downsizing. The memo is part of a process involving the White House budget office and the State Department trading proposals and suggestions.

Reports of steep cuts already had Democrats on Capitol Hill reeling.

Senator Jeanne Shaheen of New Hampshire, the top Democrat on the Foreign Relations Committee, said in a statement on Monday that the cuts “would leave our country alone and exposed and allow China and Russia to fill the vacuum made vacant by this administration.”

“Why in the world would we cut funding for NATO at a moment when war is raging in Europe and security threats on the continent grow?” she added.

Senator Brian Schatz of Hawaii, a Democrat on the appropriations committee, said: “While ultimately Congress controls the purse strings, recent reports about the administration’s plan to gut State Department personnel, U.S. presence overseas and foreign assistance are deeply troubling. These cuts don’t make America safer, they risk our security.”

“I want to hear from Secretary Rubio directly,” he added.

A budget copy of the memo began circulating in Washington in recent days. The Washington Post reported details of the memo earlier on Monday.

The State Department had no immediate comment.

The memo states that the State Department will request a $28.4 billion budget in fiscal year 2026, which begins Oct. 1. That figure is $26 billion less than what was on the books for fiscal year 2025, according to the document.

The administration intends to claw back some funds for the current fiscal year as well, according to the memo. Mr. Marocco and Mr. Pitkin wrote that the Trump administration would seek to reclaim approximately $20 billion in unspent funds from fiscal year 2025 to return to the Treasury.

Among other cuts, the memo proposes keeping a pay and hiring freeze through fiscal 2026, with the exception of any hires needed to take over foreign aid programs inherited from the U.S. Agency for International Development, which is being disbanded. Overall, the memo seeks to cut foreign aid spending by more than half of current budget levels for the State Department and U.S.A.I.D.

Though Mr. Rubio promised last month that the State Department would continue administering a number of lifesaving assistance programs, the Trump administration has quietly canceled some of those initiatives in recent weeks.

The only funding for global health programs that the State Department envisions preserving is $2.9 billion for H.I.V. treatments provided through the President’s Emergency Plan for AIDS Relief; $687 million for interventions for diseases like tuberculosis and malaria; $200 million for global health security; and $800 million for the Global Fund, distributed at a rate of $1 for every $4 other donors provide. The Global Fund is an international organization that finances disease treatment and prevention.

All other programs — including those to tackle neglected tropical diseases, provide vaccines to children in poor countries and preserve maternal and child health — would be cut.

The memo offers fewer details about the cuts to humanitarian aid. It outlines $2.5 billion for a new Bureau for Humanitarian Assistance at the State Department, and $1.5 billion in emergency migration and refugee assistance that President Trump can use “to address humanitarian emergencies.”

The memo also proposes a one-year freeze for a key narcotics control program, rationalizing the suspension of funds by noting that the program has an unspent $1.4 billion on hand that should cover that period.

Additionally, it envisions creating a roughly $2 billion America First Opportunities Fund at the Treasury, which would give the Trump administration latitude to “provide targeted support for economic and development assistance for enduring and emerging Trump administration priorities.”

Stephanie Nolen contributed reporting.