Capitol Hill aides confirmed details of the upcoming blueprint on the condition of anonymity to discuss information that's not yet been made public.
Trump's first major fiscal marker will land in the agencies one day before his first address to a joint session of Congress. For Trump, the primetime speech is an opportunity to refocus his young presidency on the core economic issues that were a centerpiece of his White House run.
The upcoming submission covers the budget year starting on Oct. 1. But first there's an April 28 deadline to finish up the unfinished spending bills for the ongoing 2017 budget year, which is almost half over, and any stumble or protracted battle could risk a government shutdown then as well.
The March release is also expected to include an immediate infusion of 2017 cash for the Pentagon that's expected to register about $20 billion or so and contain the first wave of funding for Trump's promised border wall and other initiatives like hiring immigration agents.
The president previewed a boost in military spending during a speech Friday to conservative activists, pledging "one of the greatest build-ups in American history."
"We will be substantially upgrading all of our military, all of our military, offensive, defensive, everything, bigger and better and stronger than ever before," he said.
In an interview with Fox News Channel's "Sunday Morning Futures," Treasury Secretary Steven Mnuchin said cuts to Social Security and Medicare would not be part of the administration's first budget. Trump's priority is passing legislation to reduce middle-class and corporate taxes, he said.
As a candidate, Trump promised to leave major entitlements untouched, breaking with some Republican leaders who believe the costly programs need to be reformed.
The White House budget office issued a statement confirming that an interim budget submission will be released in mid-March but declining to comment on an "internal discussion."
"The president and his Cabinet are working collaboratively to create a budget that keeps the president's promises to secure the country and restore fiscal sanity to how we spend American taxpayers' money," said Office of Management and Budget spokesman John Czwartacki.
Czwartacki said that the March submission would only address agency operating budgets funded by Congress and that proposals on tax reform and so-called mandatory programs — they include food stamps, student loans, health programs and farm subsidies — will be released later.
By increasing defense and leaving Medicare and Social Security untouched, the Trump final budget plan is sure to project sizable deficits. In the campaign Trump promised huge tax cuts but top GOP leaders like House Speaker Paul Ryan of Wisconsin don't want this year's tax reform drive to add to the budget deficit.