"Congress has the freedom to approve this resolution and I have a duty to veto it," Trump said from the Oval Office before officially postponing the measure to Congress without his approval.
Trump said the resolution, which overturned the national emergency, "endangered countless Americans".
"There have not been too many cases of emergency greater than what we have" at our borders, he said.
Trump was surrounded by Friday's Customs and Border Protection officials and surviving family members of those who lost their lives due to undocumented immigrants. Attorney General William Barr was also in the President's veto event.
While some legislators ̵
"The President acted well in his discretion in declaring a national emergency concerning the southern border," said Attorney General Stephen Boyd, exposing the legal basis for the proclamation under the National Emergency Law and the additional statutory authorities, which largely follow an internal memo issued by the Legal Department at the Department of Justice.
"The President's urgent proclamation reasonably described the current situation as" border security and a humanitarian crisis "," adds Boyd. "The border crisis … can be considered an emergency even if it is not completely new."
Twelve Republican senators gathered Thursday to deliver the powerful reproach after expressing concern that Trump's use of the national emergency The declaration as the end of Congress violates the separation of powers and constitutes a negative precedent that a future future democratic president could follow to guide their agenda unilaterally.
Trump rejected requests by some Senate Republicans to accept a compromise that would reduce his national emergency powers and instead framed the vote not as a matter of constitutional concerns, but rather as a litmus test on border security .
The approach – particularly the threats of re-election repercussions – have blocked defections by several Republicans in preparation for re-election in 2020, but in the end they have not prevented the Senate from approving the resolution.
Trump tweeted about the political advantage he expects from those who support him will receive.
"I would like to thank all the great Republican senators who bravely voted for Strong Border Security and the WALL. This will help stop crime, human trafficking and drugs entering our country. Look, when you get back in your Been, they'll love you more than ever! "Trump tweeted Friday.
Trump's veto refers the resolution to the House of Representatives, which should resume it after the week – a congressional recess. The Chamber is not expected to have two-thirds of the chamber support needed to override the President's veto.
This story has been updated with further developments on Friday