Reflecting back on his past two, tumultuous years in the White House, he said: "Had I known then what I know now, I would've just asked Putin to give the job to Hillary instead".
"I think in the end we're going to be very successful with the lawsuit", Trump said.
A coalition of 16 US states led by California sued Trump and top members of his administration on Monday to block his decision to declare the emergency.
Trump says he expects to lose some of the initial court cases filed against his declaration but ultimately prevail with a favorable ruling by the Supreme Court, reversing the lower court decisions.
All the states involved in the lawsuit have Democratic attorneys general.
Trump declared a national emergency last Friday despite no evidence of an immigration crisis. The move allows the president to bypass Congress to use money from the Pentagon and other budgets. The argument at the core of each lawsuit is similar: Trump exceeded his authority and circumvented Congress in an attempt to achieve his signature campaign promise for an emergency that, plaintiffs argue, doesn't exist. Another suit was filed Tuesday in the Northern District of California by the American Civil Liberties Union.
Sierra Club et al. vs. Trump et al.
Democrats are also planning to introduce a resolution disapproving of the declaration once Congress returns to session and it is likely to pass both chambers. The lawsuit asks the court to permanently prohibit the Trump administration from diverting the funds from elsewhere in the government, or to build a wall without Congress appropriating money for that objective. I don't like this.
Khloe Kardashian responds to Tristan Thompson’s alleged infidelity
Since the news emerged, Keeping up with the Kardashians fans have been taking to social media to blast both Thompson and Woods . A source told the outlet that there's little chance of reconciliation, saying, "She has had enough".
"I am strongly opposed to the president invoking his national emergency powers".
Trump says the wall is necessary to thwart illegal migrants from entering the country and to interdict drug shipments.
Democrats quickly seized on the move as an example of executive overreach.
The estimated cost for a San Francisco-to-Los Angeles train has more than doubled to $77 billion.
Sixteen states, landowners along the border and an environmental group have sued Trump to try to keep him from carrying out his plan to tap $8 billion in government funds now allocated for other purposes to build more than 320 kilometers of wall along the 3,200-kilometer U.S.
The emergency declaration is already being challenged by an investigation by the House Judiciary Committee, and in the courts with a lawsuit from 15 states led by California. He said the state would focus on completing a shorter segment in the state's Central Valley while seeking new funding sources for the longer route.