White House officials looked at Trump's campaign speeches and "America First" pledges as they crunched the numbers, Mulvaney said.
"We turned those policies into numbers," he said, explaining how the document mirrored pledges to spend more on the U.S. nuclear weapons arsenal, veterans' health care, the FBI, and Justice Department efforts to fight drug dealers and violent crime.
The Department of Homeland Security would get a 6.8 percent increase, with more money for extra staff needed to catch, detain and deport illegal immigrants.
Trump wants Congress to shell out $1.5 billion for the border wall with Mexico in the current fiscal year — enough for pilot projects to determine the best way to build it — and a further $2.6 billion in fiscal 2018, Mulvaney said.
The estimate of the full cost of the wall will be included in the full budget, expected in mid-May, which will project spending and revenues over 10 years.
Trump has vowed Mexico will pay for the border wall, which the Mexican government has flatly said it will not do. The White House has said recently that funding would be kick-started in the United States.
The voluminous budget document will include economic forecasts and Trump's views on "mandatory entitlements" — big-ticket programs like Social Security and Medicare, which Trump vowed to protect on the campaign trail.