Video report by ITV News correspondent Martha Fairlie
Donald Trump insisted the United States is "full" during a visit to a California border city.
On a visit to Caleixco, a US city on the border with Mexico, Trump met with immigration agents and insisted the country's immigration system was under too much strain.
Trump's remarks come after California and 19 other states filed lawsuits against the President over his declaration requested a court order stop money from being diverted to fund the project.
Trump, who even vetoed a congressional vote and some opposition from his own party, said the move was necessary.
At a border security briefing, Trump said: “There is indeed an emergency on our southern border", adding there had been a surge in the number of illegal crossings into the country.
He added: “There is indeed an emergency on our southern border,” Mr Trump said at a border security briefing, adding that there has been a sharp rise in illegal crossings.
“It’s a colossal surge, and it’s overwhelming our immigration system. We can’t take you any more. Our country is full.”
Although his border wall project - one of the key promises of his election campaign - remain unbuilt, the President said at least 400 miles of barrier would be erected in the next two years.
“The crisis is a direct result of the obstruction by Democrats,” the president claimed.
Trump also denied he had changed his mind about closing the border down with Mexico, an idea he has toyed with on several occasions.
“Mexico has been absolutely terrific for the last four days,” the president said as he left the White House.
“I never changed my mind at all. I may shut it down at some point.”
Mr Trump, who wants to return to illegal immigration as a key 2020 re-election issue, also used Twitter earlier Friday to claim that he could revive his threat to shut the border, a move that fellow Republicans warned would have a devastating economic impact.
“If for any reason Mexico stops apprehending and bringing the illegals back to where they came from, the US will be forced to Tariff at 25% all cars made in Mexico and shipped over the Border to us. If that doesn’t work, which it will, I will close the Border,” Trump tweeted.