President Trump speaks on border security and government funding at the White House (Picture: PA).
Donald Trump has declared a national emergency at the US-Mexico border following a stinging budget defeat.
The US President moved to secure more money for his long-promised wall by exercising a broad interpretation of his presidential powers that is certain to draw stiff legal challenges.
President Trump signed the declaration to justify diverting billions of federal dollars from military construction and other purposes after Congress approved only a fraction of the money he had demanded.
In his emergency proclamation on Friday, the US President painted a dark picture of the border as "a major entry point for criminals, gang members, and illicit narcotics" and one that threatens "core national security interests".
Overall, though, illegal border crossings are down from a high of 1.6 million in 2000.
His declaration instantly transformed a contentious policy fight into a foundational dispute over the separation of powers enshrined in the US Constitution, spurring talk of a congressional vote to block President Trump and ensuring that the president and Democrats will continue fighting over the border wall in Congress, the courts and on the campaign trail.
The stand-off over border funding had led to the longest government shutdown in history. To avoid another shutdown, President Trump reluctantly signed a funding bill on Friday which included just 1.4 billion US dollars of the 5.7 billion US dollars he had demanded for the wall.
The US President announced the declaration in a free-wheeling, 50-minute Rose Garden news conference that included a long preamble about his administration's accomplishments.
He jousted with reporters and delivered a sing-song prediction about the fate of the order as it winds its way through the legal system before potentially ending up at the Supreme Court.
"Sadly, we'll be sued and sadly it will go through a process and happily we'll win, I think," he said.
The text of President Trump's proclamation cited an increase in families coming across the border and an inability to detain families during deportation proceedings - not drugs or violence as the president outlined in his press conference.
The top two Democrats in Congress said they would use "every remedy available" to oppose what they cast as an unlawful measure.
"The President's actions clearly violate the Congress's exclusive power of the purse, which our founders enshrined in the Constitution," House Speaker Nancy Pelosi and Senate Minority Leader Charles Schumer said in a joint statement.
The President defended his use of an emergency declaration, saying that other presidents had done the same.
Other presidents have used emergency powers, but not to pay for projects that Congress would not support.
The money in the spending bill President Trump signed would finance just a quarter of the more than 200 miles (322km) of barrier he wanted this year.
To bridge the gap, he announced that he will be spending roughly $8 billion on border barriers - combining the money approved by Congress with funding he plans to repurpose through executive actions, including the national emergency.
Money for hundreds of military construction projects around the country was potentially targeted, and Democratic congressional aides were wary that projects sponsored by Democratic politicians might be disproportionately hit.