President Donald Trump, heading to Texas on Day 20 of a partial government shutdown, promised on Thursday to hold firm to his pledge for a border wall.

The president showed no signs of relenting on his demand for more than $5 billion to build part of a barrier on the border. In a string of tweets in part responding to a morning television host, Trump said "I won't" cave on the wall demand.

Trump tweet

The message came a day after talks to reopen nine federal departments crumbled. Trump walked out of a meeting with House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer after the top U.S. representative rejected his request for border wall money. The breakdown has massive stakes for the hundreds of thousands of federal workers who will start to miss paychecks Friday if lawmakers fail to fund the government. If the standoff continues Friday, the shutdown will have tied as the longest in U.S. history.

Trump flew to McAllen, Texas, on Thursday morning to draw attention to what he claims is a "humanitarian crisis" at the southern border. The president has used horrific tales of murder and drug abuse to make his case for a wall — prompting Democrats to accuse him of falsehoods, exaggerations and fear mongering for political purposes.

Trump has teased the possibility of declaring a national emergency to build the border barrier without congressional approval. On Thursday, he argued he has an "absolute right" to do so, but the move would likely face a swift challenge in the courts. He could potentially use the journey to McAllen, a busy border area, as part of his justification for the action.

"If [a deal with Congress] doesn't work out, probably I will do it. I would almost say definitely," Trump said of declaring a national emergency as he left the White House for Texas.