Trump To Spend More On Military
The blueprint will increase defence spending by $54bn (£43bn) but seeks to recoup that sum through deep cuts elsewhere, including to foreign aid.
Mr Trump's plan leaves large welfare programmes untouched, despite Republican calls for reform.
The president has consulted government agencies about his plans and will present his budget to Congress in May.
Between now and then, he needs to identify where the agencies can make savings and work out what he does with tax reform.
Republican John McCain said the $603bn defence budget - which was outlined by White House officials - would be insufficient.
Speaking at the White House during a meeting with state governors on Monday morning, Mr Trump said: "We're going to do more with less and make the government lean and accountable."
The president, who vowed to increase military spending and preserve welfare programmes during his campaign, said the budget will focus on "military, safety, economic development".
"It will include an historic increase in defence spending to rebuild the depleted military of the United States of America at a time we most need it," he said.
Military spending has declined in recent years due to budgetary battles in Congress that led to a spending freeze on defence.
However, it is still not uncommon for Congress to approve procurement of tanks, aircraft and ships that the Pentagon says it doesn't even need.
Mr Trump's proposal would return the US closer to wartime spending.
He also said he would spend "big" on infrastructure like roads and rails, but he has not yet revealed his tax plans.
Mr Trump pledged to cut taxes during his presidential campaign, which would probably add to the national debt, a figure that could hit $20 trillion on his watch.