Bernie Sanders described the budget proposals as "morally obscene"
Donald Trump has revealed plans to slash environmental and foreign aid budgets to fund a $54bn (€50bn) increase in military spending.
In the new administration's first budget proposals, the White House has outlined plans to cut more than $10bn from the Department of State and USAID - an agency which works to fight poverty across the globe.
Mr Trump has also announced a planned 31% ($2.6bn) reduction in the Environmental Protection Agency's budget - a cut that would lead to the loss of a fifth of the organisation's workforce.
The proposal would discontinue the agency's Clean Power Plan, a policy announced in 2015 by former president Barack Obama to reduce carbon pollution from power plants.
It would also end funding for international climate change programs, climate change research and partnership programs.
Meanwhile, Mr Trump's "America First" draft budget sets aside $639bn for the Department of Defense - a $52bn year-on-year increase.
Mr Trump said the boost has been announced to "rebuild the US Armed Forces" after "arbitrary depletion" under Mr Obama.
He said: "We must ensure that our courageous servicemen and women have the tools they need to deter war, and when called upon to fight, do only one thing - win."
The budget adds that the additional funding would "provide the resources needed to accelerate the defeat of ISIS" and back efforts to counter "complex threats from sophisticated state actors and transnational terrorist groups".
The planned increases in military spending, which include an extra $2.8bn for homeland security, are the largest since Ronald Reagan's presidency in the 1980s.
To prop up the increase, Mr Trump also plans to cut the Department of Health and Human Services' budget by 18% ($15.1bn) and decrease education funding by 13% ($9bn).
It also proposes the elimination of funding for the Corporation for Public Broadcasting, the Institute of Museum and Library Services and the National Endowment for the Arts / Humanities.
The President's budget director, Mick Mulvaney, described the spending plans as a "hard power budget".
He said: "The President very clearly wants to send a message to our allies and our potential adversaries that this is strong power administration."
Mr Trump's spending proposals will be submitted to Congress in a series of "annual appropriations bills".
To be passed each need 60 votes in the Senate, which is marginally controlled 52-48 by the Republicans.
Senator Bernie Sanders described the budget as "morally obscene and bad economic policy".
In a statement, the Vermont senator said: "It will cause devastating pain to the very people Trump promised to help during the campaign.
"At a time of massive income and wealth inequality, when 43 million Americans are living in poverty and half of older Americans have no retirement savings, we should not slash programs that senior citizens, children and working people rely on in order to provide a massive increase in spending to the military industrial complex.
He added: "Trump's priorities are exactly opposite of where we should be heading as a nation."
A number of Democratic senators have also criticised the proposals:
$54 Billion more for military, slash diplomacy budget (why try to talk out a problem?) and elimination of Meals on Wheels. Let's Organize.— Rep. Keith Ellison (@keithellison) March 16, 2017
Democrats in Congress will emphatically oppose these cuts & urge our Republican colleagues to reject them as well. #Trumpcuts— Chuck Schumer (@SenSchumer) March 16, 2017