Prospects for wrapping up the defense spending bill for fiscal 2012 by the Dec. 16 deadline are dimming.

Defense is currently being funded through a continuing resolution along with much of the rest of the federal government. “It’s likely that the continuing resolution will be extended further, perhaps into January,” says Todd Harrison, a senior fellow with the Center for Strategic and Budgetary Assessments.

Before leaving for the Thanksgiving break, the Senate was debating the defense authorization bill. Congress returns in the final days of November, leaving little time for debate on other bills — even the must-pass defense spending bill, defense insiders say.

And while lawmakers have pledged to move every appropriations bill through Congress via the regular process, Democrats are digging in on the defense bill while Republicans are holding out on the spending bill over labor and health issues.

In addition to a delay in passing the bill, one insider thinks that the Senate version of the defense bill may skip full consideration by the Senate altogether. The House bill would be reconciled with the version passed by the Senate Appropriations Committee and then added to another bill as an amendment to pass in both chambers.

That move would provide cover for controversial items in the bill such as Lockheed Martin’s Medium Extended Air Defense System (Meads). Sen. John McCain (R-Ariz.) is seeking to kill Meads in the defense authorization bill, and would likely try to amend the Senate’s defense appropriations bill to remove funding for it.

If the bill advances outside of the regular process, attempts to remove funding might not see the light of day.

And lawmakers and defense insiders alike still point to the F-35 Joint Strike Fighter (JSF) as one of the most difficult issues to resolve between the two chambers. The Senate Appropriations Committee has proposed cutting $695 million to slow production of the fifth-generation fighter while it is still undergoing testing. And since the markup of that bill, congressional concerns about JSF testing have only deepened. The House, where support for the jet is strong, pulled just $75.7 million from President Barack Obama’s request.