Congress is on track to wrap up major spending and defense bills before calling it quits for the year, although last-minute surprises are always possible.

The Senate is expected to pass the annual National Defense Authorization Act, which cleared the House Dec. 4. The bill's provision authorizing a train-and-equip mission for Syrian rebels has emerged as a major concern for some members but that shouldn't prevent the must-pass bill from getting sent over to President Barack Obama for his signature.

Among the issues lawmakers are grappling with is the bill's lack of specified funding levels for the mission. Committee sources told Al-Monitor that a part of the program will be paid for by US allies, raising further questions about how the vetting of selected rebels can be controlled.

Lawmakers must also pass a spending bill to keep the government open past Dec. 11. The House and Senate are still ironing out differences between their various Appropriations provisions but congressional leaders are confident they can reach a long-term agreement to pay for the government through Sept. 30, even though some conservatives prefer a short-term spending bill so they can reset the clock when Republicans take over the Senate in January.