"Congress has the freedom to pass this resolution and I have the duty to veto it".
"I'm very proud to veto it", he added.
He hit his usual (exaggerated) talking points on the drugs and criminals pouring over the border and said that Democrats and Republicans could come to an accord on "catch and release" laws in "15 minutes" if the political will was there.
The president defied Speaker Nancy Pelosi, Congressional Democrats, and the "dirty dozen" Senate Republicans who joined them.
"People hate the word invasion, but that's what it is", Trump continued, calling the resolution "dangerous" and "reckless".
Mr Trump said that, since 1976, a total of 56 national emergencies have been declared but Congress has not vetoed any of them.
The emergency declaration is being challenged in court as an unconstitutional usurpation of Congress' power of the purse.
Dolphins Quarterback Ryan Tannehill Traded to Tennessee Titans
He posted a 42-46 record over six seasons, while throwing for 20,434 yards and 123 touchdowns with 75 interceptions. The Titans have agreed to a trade with the Miami Dolphins that will send quarterback Ryan Tannehill to Tennessee.
Trump insists he's on solid legal ground, however.
Trump was surrounded at Friday's event by officials from Customs and Border Protection as well as surviving family members of those who have loved ones killed by undocumented immigrants.
The president has maintained that the situation with migrants at the southern border is a national security and humanitarian crisis, while Democrats have accused him of fear-mongering.
"The President acted well within his discretion in declaring a national emergency concerning the southern border", the Justice Department argues in the letter, a copy of which was reviewed by The Washington Post.
Senator Thom Tillis, another senator up for re-election in a politically divided state, had announced last month that he would vote for the disapproval resolution.
They included Sens. Marco Rubio, Rob Portman, Susan Collins, Lisa Murkowski, Pat Toomey, Roy Blunt, Lamar Alexander, Mitt Romney, Rand Paul, Jerry Moran, Mike Lee, and Roger Wicker. He wrote an opinion piece in the Washington Post at the time arguing there would be "no intellectual honesty" in supporting executive overreach by Trump that he had opposed under President Barack Obama.
Barr also made remarks and said President Trump's emergency declaration on the issue is "firmly grounded" in the law.