In language designed to resonate with his supporters, the president claimed the bill passed by the House and Senate that would have overturned his declaration of a national emergency at the border, was “reckless”.
“As president the protection of the nation is my highest duty. Yesterday, Congress passed a dangerous resolution that if signed into law would put countless Americans in danger, very grave danger,” he said, seated behind his desk in the Oval Office. “Congress has the freedom to pass this resolution, and I have the duty to veto it.”
He added: “We’re on track for a million people rushing our borders ... People hate the word invasion, but that’s what it is.”
Earlier this week, 12 Republicans had joined with Democrats to pass a measure 59-41 to rescind the national emergency declared by Mr Trump last month in a move widely seen as a means to circumnavigate a Congress that has rejected his demand for more than $8bn (£6bn) in funding for a border wall.
The House of Representatives has already passed the bill, and the president had indicted straight away he would make use of his veto powers for the time to block the measure. “VETO,”, he said on Twitter.
Flanked by vice president Mike Pence, attorney general William Barr and Kirstjen Nielsen, the homeland security secretary, the president claimed the bill he had been to sign into law was dangerous.
The president found himself facing considerable bipartisan criticism for last month’s declaration. Democrats said Mr Trump was lying for political gain when he claimed the situation at the border amounted to a national emergency.
Both Democrats and Republicans in Congress, resented what they considered presidential overreach and his attempt to take control of powers traditionally held by Congress to fund the government. Democrats responded to Mr Trump’s move by announcing they would now try to overturn his veto.
Speaker Nancy Pelosi said the House of Representatives would take up a resolution on March 25 seeking to override his actions.
“On March 26, the House will once again act to protect our constitution and our democracy from the president’s emergency declaration by holding a vote to override his veto,” she said.
While Mr Trump suffered several defeats on Capitol Hill this week, it is unclear whether Democrats can gather up the two-thirds majority required in both chambers of Congress to overturn the veto.
Reuters said the president expressed pride in the Republicans who did not vote to support the resolution and said later he had sympathy for those who defied him, adding they did what they had to do. The White House had lobbied heavily for Republicans to back Mr Trump,
Before the signing ceremony, Mr Trump had thanked those who supported him, but also raised a veiled threat against those who did not.
“I’d like to thank all of the Great Republican Senators who bravely voted for Strong Border Security and the WALL,” Trump tweeted. “This will help stop Crime, Human Trafficking, and Drugs entering our Country. Watch, when you get back to your State, they will LOVE you more than ever before!”