President Donald Trump addressed the nation Tuesday night in an effort to convince the American public that there is a crisis at the U.S.-Mexico border, and that the best solution for this crisis is a wall. During the speech, Trump's first from the Oval Office, the president asked the Democrats to return to the White House for further meetings, saying it was "immoral" for politicians not to address the issue.

The speech came amid one of the longest federal government shutdowns in U.S. history, now at day 18. Trump and Democratic leaders in Congress are not close to a budget compromise that would reopen the government. Work for 800,000 federal employees — 380,000 are furloughed and 420,000 are working without pay — and services provided by many federal agencies hang in the balance.

Trump has requested $5.6 billion for a border wall, but Senate Minority Leader Chuck Schumer and House Speaker Nancy Pelosi say they will not make this concession.

Schumer and Pelosi spoke shortly after Trump to rebut his claims. Pelosi noted that on the first day of the new Congress, House Democrats passed Senate Republican legislation to open the government, but Trump has rejected the overture.

"The president has chosen fear," Pelosi said. "We want to start with the facts."

Talks over ending the shutdown have been at an impasse over Trump's demand for the wall. He has offered to build it using steel rather than concrete, billing that as a concession to Democrats' objections. They "don't like concrete, so we'll give them steel," he said.

But Democrats have made clear that they object to the wall itself, not what it's made of. They see it as immoral and ineffective and prefer other types of border security funded at already agreed-upon levels.

Trump will follow his prime-time address with a trip to the border Thursday, during which he will "meet with those on the front lines of the national security and humanitarian crisis," according to a tweet by White House Press Secretary Sarah Huckabee Sanders.

The administration has also discussed the idea of declaring a national emergency in order for Trump to move ahead with building the wall without needing approval from Congress, but the president did not make that declaration during his speech.

Such a move would certainly draw legal challenges, and Trump — who told lawmakers he would be willing to keep the government closed for months or even years — has said he would like to continue negotiations for now.

The Associated Press contributed to this article.