(CNN) The standoff over government spending that could lead to a partial government shutdown is over $5 billion that President Donald Trump wants to start building his border wall and to further beef up border security.

Democrats argue all the extra money -- more than $1 billion -- set aside last year for border security has not yet been spent.

The spending war boils down to a fight over the President's long-promised wall.

And that $5 billion might sound like a lot, but the US government brings in and spends trillions of dollars each year. In fact, the Congressional Budget Office predicts the government will spend about $1 trillion more than it brings in for 2019.

Most of that spending -- about 70% -- is spoken for long before it is collected via taxes. This mandatory spending funds interest on the growing national debt, Medicare and Social Security.

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