WATCH: OMB Director Vought testifies before Senate panel on Trump's 2027 budget request

Russell Vought, a key figure in the Trump administration's efforts to shrink the federal workforce, will defend the president's budget request in a congressional hearing again on Thursday.

Watch in our video player above.

President Donald Trump's funding wish list for fiscal year 2027 includes a staggering bump for defense spending — a nearly 50% increase to $1.5 trillion — to build his "dream military."

Alongside that boost to military spending are proposed cuts to non-defense spending. That includes taking aim at Biden-era green energy and infrastructure actions, billions in K-12 education, as well as pulling back from scientific research, such as a proposed 54% cut to the National Science Foundation.

WATCH: Vought defends Trump budget's proposed funding cuts to NIH, National Science Foundation

After weathering cuts last year, science groups have called on Congress to reject the president's proposed cuts to science and health agencies for fiscal year 2027.

Vought, the White House budget director, testified before a House panel Wednesday.

Watch the full House hearing below.

The president's budget request is not final. But it does signal the Trump administration's priorities for the coming fiscal year.

Congress holds the "power of the purse," per the U.S. Constitution — a fact that Senate Appropriations Chair Susan Collins, R-Maine, repeated in a statement earlier this month.

"While there are some improvements [in the new proposal] over last year's domestic discretionary budget request, … the request has several shortcomings," Collins wrote.

Even though Trump has tried to exert more authority over spending in his second term, it's up to both chambers to revise and approve the final budget in the coming months.