The United States Air Force is accelerating investment in space as Chinese advancements threaten to penetrate American systems in the previously uncontested domain, top service officials said during a congressional hearing Tuesday.

Speaking before the Senate Armed Services Committee, Air Force secretary Heather Wilson and chief of staff General David Goldfein both identified China's space innovation and "rapid growth" in military capabilities among their top concerns facing the service in the coming years.

"Some of the work they're doing in space, it's very aggressive," Goldfein said. "We built our space architecture in an era when space was a rather benign domain, so … we're very focused on taking some bold moves in this budget to increase our ability to defend what we have in space."

Though Goldfein nodded to Russian gains in space capabilities, he noted Moscow doesn't have the same "economic base" as Beijing that has allowed for such rapid advancements.

The remarks come amid an ongoing debate among lawmakers and Trump administration officials over the creation of a space command as a separate military branch housed within the Air Force, just as the Marine Corps is structured under the Navy. The House scrapped a Space Corps proposal last year after pushback from the Pentagon and Senate members, but the issue has received renewed attention since President Donald Trump raised the idea last month.

Wilson said while the service is "open to discussing ideas that people have in this realm … the most important thing is not the organization, but what we actually do" to defend the United States and to "make clear to any adversary that if they take us on in space, we will prevail."

The U.S. Air Force plans to invest $44.3 billion in space systems over the next five years, marking an 18 percent increase over the $37.5 billion five-year plan submitted last year. The service's fiscal 2019 budget request of $156.3 billion also includes a 33 percent increase in spending on space satellites, rocket launchers, and capabilities to counter space attacks as China and Russia continue to make advancements.

"We are building a more lethal and a more agile force and I think this fiscal year ’19 budget has a significant commitment to be able to defend ourselves on orbit," Wilson said. "I feel that the United States is the best in the world at space and our adversaries know it.… They are developing the capabilities to deny us the ability to freely operate in space in crisis or war. This budget represents an alignment to the American leadership."