United States President Donald Trump has confirmed he will use emergency powers to build a wall on Mexico’s border, saying “walls work”,a move that Democrats vowed to challenge as unconstitutional.

Speaking in the White House Rose Garden, the US president insisted he had no choice but to declare a national emergency to deal with what he describes as a crisis of illegal immigration.

“I am going to be signing a national emergency,” Trump said from the Rose Garden, as he claimed illegal immigration marked “an invasion of our country.”

Building the wall was a key pledge of President Trump’s campaign, but Democrats have described the emergency as a “gross abuse of power”.

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