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President Trump's decision Friday to declare a national emergency on the southern border elicited mixed reactions from members of Congress — mainly from Democratic lawmakers who vehemently disapproved of his decision.

“We’re going to confront the national security crisis on our southern border … one way or the other, we have to do it,” Trump said in the Rose Garden.

Though Congress gave Trump roughly $1.4 billion for border barriers, the amount was well below the $5.7 billion the president has said is required to build a wall. But the president is expected to use his executive authority to use other sources of funding to get a total of $8 billion to build the wall. The White House says Trump plans to tap accounts in the Treasury and Defense departments, but not money earmarked for disaster relief.

HOW TRUMP'S BORDER WALL WILL BE FUNDED

Trump said Friday that he expects legal challenges to his decision to declare a national emergency to erect barriers between the U.S. and Mexico but says he'll be vindicated.

Read on for a look at how lawmakers are reacting to the news.

Speaker of the U.S. House of Representatives Nancy Pelosi, D-Calif., said in part that Trump's emergency declaration does "great violence to our Constitution."

"The American people, the Congress and the courts must show Trump what the Constitution and separation of powers is about. Trump cannot declare a 'national emergency' whenever he wants, and spend money on his pet project. Not gonna happen!" Democratic Sen. Bernie Sanders of Vermont tweeted.

"Let’s be clear – this is not a national emergency, it is a political emergency for President Trump. Instead of working with Congress on humane, responsible, and effective border security, the President has chosen to abuse his power under the Constitution," Rep. Betty McCollum, D-Minn., tweeted.

Sen. Chris Coons, D-Del., called Trump's decision a "terrible idea."

"These powers should be used for genuine national security emergencies, not just because the president didn’t get his way," Democratic Congresswoman Lori Trahan, who represents Massachusetts' 5th congressional district, said.

Rep. Mike Levin, D-Calif., said in a statement that Trump's emergency declaration is a "clear abuse of power and likely unconstitutional."

Democratic Sen. Jeff Merkley said he's "looking forward to voting for a resolution nullifying this fake emergency declaration."

Rep. Doug Collins, R-Ga., issued a statement of support of Trump's decision.

“The crisis at our southern border demands immediate action, and I support President Trump’s commitment to securing our border and protecting our citizens. Declaring a national emergency is a serious act with deep implications, and it’s disappointing that partisan politics have brought us to this point. In acknowledging this, we also recognize the president possesses full legal authority to declare this emergency and he is not alone in his commitment to keeping Americans and migrants safe," he said.

"Congress should also take action to address the crisis that continues to endanger Americans and dismantle families by fixing loopholes in the law that encourage people to take dangerous, illegal paths into the United States," he added.

Rep. Adam Schiff, D-Calif., said in part on Twitter that "Trump is declaring a national emergency to bypass Congress, to build a wall we don’t need, to address a crisis that doesn’t exist, by claiming an authority he doesn’t have."

Republican Rep. Jim Jordan, who represents Ohio's 4th congressional district, issued a tweet of support for Trump.

"Of course it's a national emergency," he wrote in part.

Although Republican Rep. Mike Turner, who represents Ohio's 10th congressional district, said on Twitter that he "supported this funding deal as a step towards securing our border," he noted that it is "a dangerous precedent for the President to be forced to declare a national emergency because Congress refuses to provide necessary funding to protect our country."

Sen. Rick Scott, R-Fla., also tweeted support of Trump's decision.

"I applaud @POTUS' decision to put the safety of our country first and use his authority to secure our border. I traveled to the border last week and saw firsthand the dangers the border patrolmen & women face every day as they work to keep Americans safe," he tweeted.

Sen. Ted Cruz, R-Tex., tweeted in part that Democrats' "intransigence has left the president with no other choice but to take executive action."

Rep. Jason Smith, R-M.O., echoed Trump in the last in a series of tweets.

"As President Trump said before, we build walls not because we hate people on the outside, but because we love the people on the inside," he wrote.

Senate Democratic Whip Dick Durbin of Illinois said Trump's national emergency declaration serves only as a way to "fulfill his campaign promise to build a big, beautiful wall."

Senate Majority Leader Sen. Mitch McConnell, R-Ky., said in a statement that Trump's "decision to announce emergency action is the predictable and understandable consequence of Democrats' decision to put partisan obstruction ahead of the national interest."

Republican Rep. Matt Gaetz, who represents Florida's 1st congressional district, said on Twitter he is "proud" of Trump for declaring a national emergency on the southern border.

"Today, Congress took action to address the national security crisis at our southern border. This bipartisan solution is a step in the right direction & allows @POTUS to better secure the most dangerous & heavily-trafficked areas along the U.S.-Mexico border," Sen. David Perdue, R-Ga., added.

The Associated Press contributed to this report.