The NDAA is expected to get a vote in the Senate this week and be approved with bipartisan support.
Sen. Richard Shelby of Alabama, the ranking Republican member on the Senate Appropriations Committee, has told reporters the two sides are roughly $26 billion apart.
Or it could extend the shutdown deadline into the next Congress, which will convene on January 3, and when Republicans take control of the House.
That change in majority in the House would dramatically alter the dynamic for negotiations and likely make it far harder to reach a broader funding deal.
Senate Appropriations Committee Chairman Patrick Leahy, a Vermont Democrat, outlined the argument for his party in his own floor remarks on Thursday.