Congressional Republicans remained sharply divided Monday over how to fund the Department of Homeland Security, prompting White House officials to begin preparations for a potential shutdown of the agency this weekend.

“Right now, that does seem to be where we’re headed,” White House press secretary Josh Earnest told reporters Monday.

Late Monday, Senate Democrats again filibustered a Republican funding proposal for DHS because the money is tied to a repeal of President Obama’s executive actions on immigration. The House passed the bill in mid-January, and the Senate has been trying unsuccessfully since then to advance the proposal. On Monday the vote was 47 to 46, well short of the 60 votes necessary to overcome the Democrats’ procedural roadblock. The Monday vote marked Republicans’ fourth attempt to move the House bill.

In the event of a shutdown, the immediate public impact is likely to be minimal. Most security officers would stay on the job, unpaid, during a shutdown while tens of thousands of administrative staffers would be deemed “non­essential” and furloughed until a funding deal was reached.

Many Senate Republicans seized on last week’s ruling from a federal judge in Texas halting the implementation of Obama’s immigration actions as the way to keep up the fight without shutting down a critical security agency.

“We need to fund the Department of Homeland Security. We cannot shut down the Department of Homeland Security,” Sen. John McCain (R-Ariz.) said Monday evening. He repeated himself for emphasis: “I said we cannot shut down the Department of Homeland Security.”