The speech was announced after Senate Majority Leader Mitch McConnell, R-Ky., revealed Thursday that Trump will sign a federal spending deal hashed out by lawmakers to avoid another government shutdown. But Trump will also sign a national emergency declaration over the "crisis" of illegal border crossings that he has long vowed to fix with a newly constructed wall along the U.S.-Mexico border.

Trump spoke about "the national security and humanitarian crisis on our southern border" at the event, according to the White House.

President Donald Trump delivered remarks from the Rose Garden on Friday, where he announced that he will declare a national emergency in order to build a border wall .

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The deal, announced after nearly three weeks of bipartisan negotiations in Congress, provides about $1.4 billion toward physical border barriers — a fraction of the $5.7 billion that Trump has demanded must be included in any agreement to fund the government. The amount included in the deal would fund only about 55 miles of bollard fencing along the nearly 2,000-mile-long border, and Trump has said he is "not happy" about what negotiators have come up with.

Still, Trump said he will sign the deal. But Trump says he will also declare a national emergency to divert funds toward the wall, which he has promised to his base of supporters since the start of his presidential campaign in 2015.

"President Trump will sign the government funding bill, and as he has stated before, he will also take other executive action — including a national emergency — to ensure we stop the national security and humanitarian crisis at the border," White House press secretary Sarah Huckabee Sanders said in a statement Thursday afternoon.

Critics immediately accused Trump of attempting to make an end-run around Congress to unilaterally appropriate government money for the wall, which Democrats have fought against. Even some Republicans have come out against the president on the move.

"We have a crisis at our southern border, but no crisis justifies violating the Constitution," Sen. Marco Rubio, R-Fla., said in a statement.

House Speaker Nancy Pelosi, D-Calif., said that Trump's move sets a precedent that a future Democrat president could capitalize on.

"If the president can declare an emergency on something he has created as an emergency, an illusion that he wants to convey, just think about what a president with different values can present to the American people," Pelosi said at a press conference Thursday.

The move is almost certain to be met with a legal challenge. California's governor, Gavin Newsom, and attorney general, Xavier Becerra, promised to do just that if Trump goes ahead with his plan to declare a national emergency.

Newsom Becerra tweet

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