WASHINGTON — Senate Republican leaders on Tuesday took the first steps to avert a government shutdown by scheduling a vote on a temporary spending measure that would keep agencies functioning through Dec. 11.

The move marked an important breakthrough, even though Democrats were certain to block the spending bill because of a provision cutting off federal financing for Planned Parenthood.

Ultimately, the Planned Parenthood provision, prompted by the controversy over the use of aborted fetuses in medical research, is expected to be dropped from the Senate’s spending bill. That would allow the underlying legislation to move forward with bipartisan support and set up a larger showdown over spending between Republican leaders and President Obama later this fall.

Still, the Senate majority leader, Mitch McConnell, Republican of Kentucky, urged Democrats to adopt the measure and accused them of pushing the country to the brink of a government shutdown when the fiscal year ends Sept. 30, in a bid to strong-arm Republicans into accepting spending increases.