In short, Rubel sees little chance of success on Trump's defense request as it currently stands. "His budget is likely to be dead on arrival," the analyst said.
The president will likely provide more clarity on his spending priorities and defense policy on Tuesday evening during his formal address to Congress.
According to the Committee for a Responsible Federal Budget, non-defense discretionary spending represents only 15 percent of the budget and 5 percent of spending growth over the next decade.
"Getting that much money that quickly from that small a share of the budget I think will be challenging," said Marc Goldwein, a senior vice president and policy director for the CRFB, a non-partisan think tank focused on budget issues. He pointed out that some of the non-defense discretionary spending goes to core functions of government as well as areas such as the Department of Homeland Security.
Goldwein expects it would be easier for the Trump administration to focus on the mandatory part of the budget and use those areas for savings. "The mandatory budget is huge and most of the health and retirement parts are growing rapidly," he said.
As an example, Social Security, Medicare, Medicaid and other health programs make up about half of the federal spending this year and are projected by the CRFB to be responsible for about two-thirds of spending growth over the next decade.
However, if the Trump administration were to make cuts to entitlement programs, such as Social Security and Medicare, it could trigger more resistance particularly from Democrats. So far the administration has maintained it doesn't plan cuts to these major entitlement programs.
Trump said Monday the hike in defense spending will be offset by "finding greater savings and efficiencies across the federal government. We're going to do more with less and make the government lean and accountable to the people."
The administration is expected to make major cuts in funding to the Environmental Protection Agency. Also, foreign aid cuts are possible.