President Trump announced the speech on Monday afternoon, stating on Twitter: "I am pleased to inform you that I will Address the Nation on the Humanitarian and National Security crisis on our Southern Border".
In a televised rebuttal, Democratic leaders accused the president of holding the American people hostage.
Trump's prime-time address, scheduled for 9 p.m. ET, will be the Republican president's latest attempt to persuade Democrats to back his barrier on the southern border. Hundreds of thousands of federal workers are going without pay, and government disruptions are hitting home with everyday Americans.
And on Tuesday Rep. Mac Thornberry of Georgia, the top Republican on the House Appropriations Committee, came out against the idea of reprogramming Pentagon funds to build the wall, saying he was 'opposed to using defense dollars for non-defense purposes'.
Mr Trump is backed by most of his party, though on Tuesday moderate Republican Senator Lisa Murkowski of Alaska joined Democrats in calling for an end to the shutdown before the border wall issue was resolved.
The president said children illegally brought into the USA are "used as human pawns by vicious coyotes and ruthless gangs", while women and children are "the biggest victims by far of our broken system". The White House is reportedly asking networks to cover a speech by Trump following the border visit.
Instead, he will try to make the public case for his $5.6 billion border wall, a demand that is the heart of a standoff that has led to a partial government shutdown.
There is an obvious solution: separate the shutdown from the arguments over border security.
"President Trump has appealed to fear, not facts". Such a step, however, would likely face an immediate legal challenge.
Mr Trump, who has long railed against illegal immigration at the border, has recently seized on humanitarian concerns to argue there is a broader crisis that can only be solved with a wall along the US-Mexico border.
Trump is expected to discuss what he calls a "humanitarian and national security crisis", although reports conflict about whether he will actually declare an emergency, as he has previously threatened.
Both Trump and the Democrats have agreed there is a crisis at the border.
America would be "safer than every before" under the proposal, which includes "cutting-edge technology for detecting drugs, weapons, illegal contraband and many other things", he said.
House Majority Leader Steny Hoyer said the House Democratic leadership had not yet worked out a strategy for how to respond if Trump declared a national emergency in to circumvent Congress and build the wall.
The number of illegal border crossings is down from 1.6 million in 2000 to less than 400,000 previous year. But even if blocked, Trump could claim to his base that he had done what he could, while ending the damaging government shutdown. We can reopen the government AND continue to work through disagreements about policy.
The unexpected length of the shutdown has raised the prospect that Trump would begin to lose support among Republicans anxious to reopen the government and doubtful of the White House strategy.