Last week, the broader gun package received 68 votes, including 16 from Republicans, to bring it to the Senate floor.

CNN: Senate gun law proposal lacks enough support now

Obama had pushed for Congress to include both the expanded background checks provision and the weapons ban in any gun package.

CNN: Senate rejects expanded gun background checks

In debate expected to last two weeks, senators will consider efforts by both sides to either expand or weaken the gun package.

CNN: Gun lobby may emerge victorious when smoke clears