WATCH: President Trump SLAMS Reporter Over Steel Vs. Concrete Border Wall

President Trump stood firm Friday on his demands for a border wall after the second White House meeting with congressional leaders this week broke up with no apparent deal, warning Democrats the partial government shutdown could last "years" and saying he could even declare a "national emergency" to bypass Congress if necessary.

“We can call a national emergency [to build a border wall] because of the security of our country,” Trump told reporters in the Rose Garden, during a lengthy and impromptu press conference.

“I may do it,” he said, before adding, “If we can do it through a negotiated process, we’re giving it a shot.”

The press conference underscored how far apart both sides are, even as Trump called the meeting "productive" and suggested the standoff could end soon -- or not. He indicated he was not shifting on his demand for more than $5 billion for funding for a wall on the southern border, saying it was necessary as the border is a "dangerous, horrible disaster."

"This is national security we’re talking about, we’re not talking about games," he told reporters. “We're not playing games, we have to do it."