"I didn't need to do this," Trump said of the national emergency declaration, adding, "I just want to get it done faster, that's all."
During the presidential campaign, Trump promised to build a wall along the entirety of the US-Mexico border to help prevent undocumented immigration and the influx of drugs from Mexico.
Trump ended the shutdown in late January by signing a bill that temporarily funded the government and he's set to sign a new funding bill on Friday.
The new bill includes just $1.4 billion for physical barriers on the border, much less than the $5.7 billion the White House was seeking. The shortfall is part of his justification for declaring the national emergency. The declaration was the culmination of threatening to use his emergency powers to get funding for the border wall for weeks.
Democratic leaders on Friday denounced Trump's declaration as "unlawful."
In a joint statement, House Speaker Nancy Pelosi and Minority Leader Chuck Schumer said, "The President's actions clearly violate the Congress's exclusive power of the purse, which our Founders enshrined in the Constitution. The Congress will defend our constitutional authorities in the Congress, in the Courts, and in the public, using every remedy available."
In recent weeks, some prominent Republicans such as Sen. Marco Rubio and Sen. Chuck Grassley have also expressed concerns about the precedent Trump will set by declaring a national emergency and warned that he will face opposition the courts.
Trump alluded to this during his Friday announcement, stating he's likely to be "sued."
"I expect to be sued," Trump said.
The president's statement that he "didn't need to" declare the emergency could come up during any legal battles that might follow his big announcement, according to some legal experts.
In the past , national emergencies have often been declared to impose sanctions on people involved in human rights abuses in various parts of the world, particularly Africa and Central America.
