"Now that the television networks have made a decision to air the President's address, which if his past statements are any indication will be full of malice and misinformation, Democrats must immediately be given equal airtime", Democrat leaders Senator Chuck Schumer and House Speaker Nancy Pelosi said in a statement last night, even as various liberal quarters demanded that Trump's speech should be subjected to a delayed telecast to enable instant fact-checking given his propensity for lies and dissembling.
He noted that the networks declined to air past presidents' addresses, including one from former president Barack Obama.
Trump's speech is set to be followed by a rebuttal from House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer, who oppose the wall and have called on Trump to end the shutdown. But Trump has not budged on his demands for $5.7 billion in wall funding, and Democrats have not moved from their opposition, while many Republicans watch anxiously from the sidelines.
Floodlights from the United States illuminate multiple border walls on January 7, 2019, as seen from Tijuana, Mexico.
The prototypes for Trump's border wall are seen behind the border fence between Mexico and the United States, in Tijuana, Mexico.
Mick Mulvaney, Trump's acting chief of staff, told NBC's Meet the Press program that agreeing to a steel separation would allow Democrats to stick to their refusal to fund a wall.
Democrats have repeatedly slammed the proposed wall but have remained vague about counter-proposals that would curb illegal immigration.
The number of illegal border crossings is down from 1.6 million in 2000 to less than 400,000 past year.
The White House has not said why the situation constitutes a national emergency.
"Now that the television networks have chose to air the President's address, which if his past statements are any indication will be full of malice and misinformation, Democrats must immediately be given equal airtime", they demanded in a joint statement on Monday night.
After meeting with Democrats over the weekend, the White House issued a series of budget demands, including a new request for $800,000 for humanitarian needs.
A spokesperson for George W Bush said that he never discussed the border wall with Mr Trump.
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.
Last week, Democrats who took control of the House passed a bill to reopen the government without wall funding.
A National Park Service ranger looks out onto the city from Trump International Hotel's historic clock tower, which remains open and staffed by the National Park Service despite the partial government shutdown.
With Trump heading to the border on Thursday, few saw a speedy path to resolution for the partial shutdown, which has furloughed 380,000 federal workers and forced an additional 420,000 to work without pay. Two Guatemalan children have died in border custody, while images of border patrol officers firing tear gas at migrants have raised the ire of critics.