Foreign aid, which accounts for roughly 1% of the federal budget, is expected to be high on the list of areas to cut.
This includes military aid, debt relief, funds for long-term development programs, and also emergency aid.
The US is by far the biggest donor to humanitarian crises in terms of financial contributions. The country donated roughly $6.4 billion -- or 29% of the $22.1 billion spent globally -- for emergencies alone in 2016, a spokesman for the UN's Office for the Coordination of Humanitarian Affairs (OCHA), which oversees international emergency relief efforts, told CNN.
This money is given directly to governments or though multilateral institutions like the UN High Commission for Refugees, the children's charity UNICEF and the World Food Programme.
Foreign aid cut comes at dire time
International charities and humanitarian agencies contacted by CNN say that the US policy shift could not have come at a worse time.
There are currently more refugees in the world than at any time since World War II with around 65 million people displaced, according to the UNHCR, fleeing war and terrorism from several conflicts including Syria and Iraq.
There is famine in South Sudan, caused by the civil war there. Famine also threatens northern Nigeria, Yemen and Somalia. An estimated 22 million people are in urgent need of aid in these four countries alone.
Gayle Smith, the last United States Agency for International Development (USAID) Administrator under former President Barack Obama, expressed concern over the effects that cuts could have on emergency assistance from the US.
"If we were to significantly recede, it would be a matter of life and death for a lot of people," Smith told CNN.
Jan Egeland, Secretary General of the Norwegian Refugee Council, also expressed dismay over the proposed cuts.
"How could this be justified in today's world where over 65 million people are displaced, and we are faced with multiple humanitarian crises?" he told CNN. "To abandon the vulnerable for armaments would not make America greater but would make her smaller".
John Glaser, an Associate Director of Foreign Policy Studies at the CATO Institute, said cuts were not likely to significantly worsen the plight of people facing famine and war, because a lot of the aid comes in the form of military aid to foreign countries.
"While cutting the foreign aid budget may generate some gaps in resources for people in need, US foreign aid largely does not target the most in need," Glaser told CNN.
Trump: It's about public safety
Trump described his budget blueprint
as "a public safety and national security budget" on Monday.
"With 20 trillion dollars in debt, the government must learn to tighten its belt," Trump said.
The budget blueprint would have to be approved by Congress and it's unlikely to be passed without changes.
While foreign aid has long been a target for many conservatives, cuts to these programs are unlikely to get the Trump administration close to the $54 billion in proposed overall cuts.
"Yes, it is a fairly small part of the discretionary budget, but it is still consistent with what the President said," Office of Management and Budget Director Mick Mulvaney said of the foreign aid cuts
. "We are taking his words and turning them into polices and dollars."
The budget, one OMB official said
, expects "the rest of the world to step up in some of the programs this country has been so generous in funding" over the years.
President Trump signaled his intention to slash foreign aid in his June 2015 speech announcing his candidacy. He said the United States should "stop sending foreign aid to countries that hate us" and to spend the funds to "invest in our infrastructure ... our tunnels, roads, bridges, and schools." In August, he said he would end "our current strategy of nation-building" abroad.
Generals weigh in too
Concern about aid budget cuts is not limited to the offices of aid agencies and international charities.
On Monday, 121 retired US generals and admirals, including Ret. General David Petraeus, the former CIA director, signed a letter to Congress
calling for foreign aid to be ring-fenced in the budget.
"The State Department, USAid, Millennium Challenge Corporation, Peace Corps and other development agencies are critical to preventing conflict and reducing the need to put our men and women in uniform in harm's way," they wrote.
"Foreign Aid is not charity. We must make sure it is well spent, but it is less than 1% of budget & critical to our national security." said Republican Sen. Mario Rubio in a tweet.
Aside from emergencies like earthquakes, war, floods and famine, the US is also the biggest donor by far to global health efforts, contributing roughly $2.6 billion to basic health projects through USAID in 2015 alone.
The US was heavily involved in combating the recent Ebola crisis in West Africa. Had there not been the global response there could have been an international pandemic.
Aid agencies wait and see
Where exactly Trump proposes to make the cuts will be revealed over the coming weeks.
The UN and its partners estimate it needs $22.2 billion in 2017
to meet the needs of those countries around the globe most in crisis. Even in good years when aid money flows, the UN targets are rarely met.
An official from one of the larger UN agencies, which depends on voluntary donor funding and asked not to be named, told CNN the biggest concern was the uncertainty.
"We don't know what to expect and that is never a comfortable position to be in," the official said.