Washington (CNN) A possible partial government shutdown is only a hand full of days away with President Donald Trump and congressional Democrats locked in a dispute over border security with no resolution in sight.

Funding expires for a number of key government agencies on December 21 at midnight. And while there is still time to avert a shutdown, so far the two sides have been unable to reach an agreement to keep the government open.

The key sticking point is how much money Congress should allocate for the President's long-promised wall at the US-Mexico border. Trump wants $5 billion, but Democrats are unwilling to agree to that and any spending bill needs bipartisan support to pass Congress, due in part to Senate rules requiring a 60-vote threshold to advance (Republicans control the chamber 51-49).

If a shutdown takes place, it would be limited in scope. That's because Congress has already funded roughly 75% of the federal government through September 2019, including the Pentagon as well as the Departments of Health and Human Services and Labor.

But that doesn't mean a partial shutdown just days before Christmas wouldn't be disruptive.

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