WASHINGTON ― A key legal change the Trump administration is seeking would enshrine a U.S. Space Force as a separate branch of the military next year ― but it could cost billions more upfront than what the Senate had planned.

Senate Armed Services Committee Chairman Jim Inhofe, R-Okla., an ally of the president, indicated Tuesday he was leaning toward the move after Vice President Mike Pence personally lobbied him to include the new force under Title 10, the section of United States code that organizes the U.S. military.

“The president is very strong on wanting to have it and wanting to do it immediately and wanting to do it, obviously, before the election ― and we’re going to try and get that done,” Inhofe said about legislation to create a new Space Force.

On Tuesday, Pence spoke at the Senate Republican caucus’ weekly lunch and met with Inhofe afterward ― ahead of the formal start of negotiations Thursday between the House and Senate over their competing versions of the 2020 National Defense Authorization Act, a massive defense policy bill.

But Inhofe remained concerned with the potential for massive added costs and how they would be absorbed by the bill because of how the costs are scored by the Congressional Budget Office, the agency tasked with estimating costs associated with legislative proposals.

CBO estimated the administration’s Space Force proposal would add $800 million to $1.3 billion in annual costs, and between $1.1 billion and $3 billion in one-time costs.

But, according to CBO’s analysis, the Senate bill doesn’t incur those costs because it doesn’t take a key step: declaring the new service into being. Instead, the Senate set a number of conditions and a one-year timeline for the Pentagon to start building the Space Force, all aimed at cutting costs and requiring the Pentagon prove it has a vision for the new branch.

Crucially, the Senate proposal would restructure certain organizations and personnel of the Air Force into the Space Force and would not authorize new military billets or civilian hires. That’s not a distinction made by the House bill.

“The problem we have with that is if [the NDAA amends] Title 10, you have a CBO scoring problem of $3.9 billion. We’re not very excited about that figure,” Inhofe said. “It’s not going to cost that, we all know that, so what’s the rush? But there seems to be one.”

“The president wants to [establish a Space Force] that leaves no doubt in anybody’s mind that we’re ahead of Russia and China, we’re concerned about space, and we are at the top,” Inhofe said. “If we have [the Title 10 change] as part of the bill, it will accomplish that ― but it’s my problem to make that part of the bill.”

For Trump, Space Force has grown from an aside in a 2018 speech to a serious push ― which military leaders say is needed to protect the U.S. space assets vital to military communications, navigation and intelligence. Trump in August reestablished the combatant command U.S. Space Command, with approval from Congress.

Space Force, if approved by the legislative body, would be the first new military service since the Air Force was created in 1947. It would be the smallest service by far, with between 15,000 and 20,000 members.

To Todd Harrison, an influential space and budget expert with the Center for Strategic and International Studies, the focus on Title 10 and the cost differences are overblown because they’re difficult to accurately extrapolate from the legislative language. Plus, a compromise bill might add the new service under Title 10 but easily skirt costs by keeping the Senate’s ban on new civilian and military hires, he said.

“The ramp-up rate is not well-defined in either bill,” Harrison said. “The Senate bill makes Air Force Space Command into Space Force with other elements to be added later, and the [House bill] creates a Space Force, but it’s not well-defined what goes in it either. It think it’s an academic distinction in terms of how they are scored.”