Congress has passed two versions of the fiscal year 2019 defense spending bill at a faster rate than it has in over a decade, but the road to negotiating a full conference bill before the end of 2018 is not yet clear, analysts said.

The Senate on Thursday voted 85-7 to approve the FY’19 Department of Defense (DoD) appropriations bill as amended, two months after the House passed its version of the bill in late June. The $675 billion legislation will now move to a conference committee where it will be debated by both chambers once the House returns to Capitol Hill after Labor Day, and a final spending bill will follow. That bill must be approved by both chambers before ultimately being signed into law by President Trump. Aerial view of the Pentagon, Arlington, VA

Budget analysts said Friday that they were watching the process with “cautious optimism,” but that several issues could still prevent a full spending bill from being passed before the end of the fiscal year.

Bryan Clark, a senior fellow at the Washington, D.C.-based Center for Strategic and Budgetary Assessments, said it may be premature to predict that the budget will be delivered on time this year.

“There’s going to be some churn that will have to be undertaken there in order to get to a final conference report,” he said, noting that it would be realistic to expect at least a short-term continuing resolution (CR) as lawmakers knock out the differences in their bills.

President Trump’s coveted Space Force could cause the process to slow, he noted. The Pentagon recently submitted a roadmap of efforts – including a new combatant command, a Special Operations Forces-like U.S. Space Operations Command, and a space development agency – that it can pursue without congressional approval ahead of any decision to stand up a brand-new military branch.

Lawmakers negotiating the final spending bill “will have to try to capture some of those costs, because they’re not going to want the DoD to go and spend money differently than was appropriated to support a Space Force idea that they came up with independent of Congress,” Clark noted.

Another issue could emerge from consolidating the two versions of the bill, said Wes Hallman, senior vice president for policy at the National Defense Industrial Association in Arlington, Virginia. The House version was passed as a standalone bill, while the Senate combined defense and domestic spending.  

Sen. Richard Shelby (R-Ala.), who chairs the Senate Appropriations Committee, told reporters Thursday that the intent is to go to conference “as soon as we can” and to keep the minibus bill signed by the Senate – which includes defense, along with health and human services, education and labor – together for more efficiency. That could prove difficult to accomplish, Hallman said.

“The fact is that domestic discretionary spending tends to be a little bit more difficult to get across the finish line than is defense alone,” he said. “There is a reason why they passed them the way they did in their respective houses, and how they put this together in the end is going to be a challenge.”

Disputes over levels of procurement – such as how many F-35s to buy or ships to put on contract – are negotiable, he noted. “The big question is on that larger strategy of how do we get this through conference.”

Hallman said he was “cautiously hopeful” about the bill’s chances of making it to the president’s desk by Sept. 30. “I think there’s a lot of motivation to make that happen,” he added. “We’re hoping that this portends a return to normal order that has lasted beyond this year, as opposed to an aberration of the trends of the last decade-plus.”

Shaun McDougall, a military markets analyst at Forecast International, a Newtown, Connecticut-based marketing and analysis firm, said the House and the Senate should be commended on the progress that has been made so far. However, they will now have to “buckle down” to get the legislation passed between Labor Day and October, when many lawmakers will focus on campaigning for the midterm elections in November.

“Everything has to get done in the next few weeks,” he said. But barring any “crazy amendments” being introduced during the conference debate, “it’s realistic that DoD could have a budget on time this year, although not guaranteed,” he added.

Contentious issues such as border funding – which the White House has previously advocated for – could slow down negotiations, he noted.