How Trump's border wall will be funded

President Trump declared a national emergency on Friday to help fund construction of a long-promised wall along the country’s southern border.

He is expected to shift around roughly $8 billion in already appropriated funds toward the initiative – which has been one of his signature campaign promises, sources with knowledge of the matter told Fox News.

This comes after the White House said Trump would sign a spending measure to fund the government – avoiding a government shutdown. That bill, which lacks the desired funds for the border wall, was approved by Congress on Thursday.

Here’s a look at where the president wants to draw some of the money for the border wall from, according to White House sources:

About $600 million will come from the Treasury Department’s drug forefeiture fund. White House sources told FOX Business that these funds are viewed as easily accessible over the near term.

Another $2.5 billion will be drawn from the Defense Department’s drug interdiction program – which is also viewed as a resource that can be tapped imminently.

The president plans to pluck $3.5 billion from the Department of Defense’s military construction budget.

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The Homeland Security appropriations bill will provide another $1.375 billion. This money will come from the bill that the president is expected to sign and not as a result of executive action.

Fox News’ John Roberts and FOX Business’ Blake Burman contributed to this report.