WASHINGTON — Lawmakers passed a two-week budget extension on Thursday, which avoids a government shutdown this week but sets up a pre-Christmas showdown over border security funding.

The continuing resolution passed the House and Senate without opposition. The extension was needed in part because funeral activities this week for former President George H.W. Bush disrupted planned negotiations on a full year budget deal.

Congress earlier this fall finalized appropriations for the departments of Defense and Veterans Affairs, meaning their operations won’t be disrupted if lawmakers can reach a deal by the new Dec. 21 budget deadline.

But a host of related agencies — including the State Department and Department of Homeland Security — could face a partial shutdown if Congress and the White House don’t reach agreement on finding levels for those agencies.

At the heart of the disagreement are plans for President Donald Trump’s proposed border wall in southern U.S. states. Trump has asked for $5 billion in funding for the project. A bipartisan Senate proposal only includes $1.6 billion for those border security efforts.

Earlier this week, Trump took to social media to complain that “we would save billions of dollars if the Democrats would give us the votes to build the wall.” In recent weeks, he has suggested the issue is important enough to warrant the disruptions a shutdown could cause.

The debate comes as thousands of active-duty troops remain deployed to southern states in support of border patrol missions.

Last week, the Department of Homeland Security asked the Pentagon to keep active-duty forces on the U.S.-Mexico border through Jan. 31. About 4,000 troops filling aviation support, military police, logistics and medical roles are expected to remain there into 2019.

It’s unclear what impact a partial government shutdown would have on that work. Federal officials can require border patrol members to continue to report to work even if their paychecks are temporarily halted.

House lawmakers were originally scheduled to leave for a holiday break this week, but will return for at least one more week to deal with the unfinished budget business. Several hearings postponed on Capitol Hill because of the Bush funeral services are also being rescheduled.

The new Congress is scheduled to be seated on Jan. 3.