The U.S. Senate passed a bill on Friday that would continue to fund the government past the end of the curent fiscal year, but would not strip funding for Obamacare.
That sets up a showdown with Republicans in the House of Representatives, who passed a government funding bill that would have also defunded the president's signature initiative, formally known as the Affordable Care Act.
Conservatives have been trying to use the must-pass bill as a way to kill or weaken 2010 Obama's health care law.
(Read more: How a shutdown actually works)
A small group of Senate conservatives tried but failed to stop the Senate from considering the bill. They argued their strategy would have kept Democrats from removing the Obamacare provision.
As the Senate debated the bill, Iowa's Tom Harkin criticized conservatives for "throwing a temper tantrum" and risking a government shutdown because they dislike Obamacare. The veteran Democrat said their ideology-driven behavior was "every bit as dangerous as the breakup of the Union before the Civil War."
Still unclear is whether Congress will approve legislation preventing a shutdown by Tuesday.
House GOP leaders have yet to determine how to win enough conservative support to pass a new bill.