Democrats were able to demand the ability to respond, and House Speaker Nancy Pelosi and Senate Minority Leader Charles Schumer are scheduled to do so, presenting a united front despite efforts by Trump to put a wedge between them - but passing on the chance to put forward a Democratic rising star.
Trump has reportedly considered declaring the border situation a national emergency, which could enable him to bypass congressional review and build his wall without its approval. Ahead of Tuesday night's speech, Trump aides went so far as to claim that 4000 suspected terrorists had been apprehended at the Southern border, forcing even he pro-administration Fox News to fact-check and say most were apprehended at airports. However, such a step would likely face an immediate legal challenges. It could potentially unlock military dollars for building the wall.
Whatever its contents, Trump is scheduled to follow up his speech with a trip to the border town of McAllen, Texas.
He will meet with Republican lawmakers at the Capitol on Wednesday. "That pickup ain't got reverse in it", he said.
With his use of a formal White House speech instead of his favoured Twitter blasts, Trump embraced the ceremonial trappings of his office as he tries to exit a political quagmire of his own making.
Mr Trump wants $5.7 billion to build a wall or fence along the Mexican border.
Trump's address came 18 days into a partial government shutdown precipitated by his demand for wall construction, which he has said is needed to keep out illegal immigrants and drugs. About a quarter of U.S. agencies have been shut down since last month and hundreds of thousands of government workers are likely to miss pay checks this week.More news: Video shows Cody Parkey's field goal tipped by Eagles DT Treyvon Hester
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The dispute over wall funding - Trump is demanding $5.7 billion U.S. to help build it - led to a stalemate in Congress over funding for parts of the government.
There have been multiple times when presidents have declared emergenices under the National Emergencies Act, although in recent years it was to impose sanctions on individuals or regimes.
Earlier, Vice President Mike Pence told ABC television that Mr Trump would lay out the "real humanitarian and security crisis at our southern border". Critics say the security risks are overblown and the administration is at least partly to blame for the humanitarian situation.
The number of Central American families coming to the border seeking asylum in the USA has risen sharply in the past year. But mostly Trump still wants his wall, which Democrats describe as immoral as well as no solution to illegal immigration. Pence said the White House counsel's office is looking at the idea. Robert Menendez said Trump is on an 'egotistical quest'. All networks carrying Trump's address have agreed to carry the Democrats' response.
"President Trump has appealed to fear, not facts".
Democrats, who ended the Trump presidency's dominance of domestic politics when they seized the House of Representatives from his Republicans in November, cried foul before a word was spoken. But GOP leaders believe they can avoid more defections to prevent Pelosi from gaining a veto-proof majority. Harrowing tales are starting to emerge from the fallout due to the shutdown, including airport security workers calling in sick because they have not been paid and therefore can not make it to work. Federal workers are about to miss a paycheck.
Trump has said he can relate to the plight of the federal workers who aren't getting paid, though he acknowledged they will have to "make adjustments".