US President Donald Trump. File photo
US President Donald Trump has demanded funding for his long-promised US-Mexico border wall to halt "a growing humanitarian and security crisis".
But in his first TV address to the nation from the Oval Office, Mr Trump did not declare a national emergency to bypass Congress and build the barrier.
In a televised rebuttal, Democratic leaders accused the president of holding the American people hostage.
Both sides are trying to gain an edge amid an 18-day government shutdown.
In an eight-minute address on Tuesday night carried live by all the major US television networks, Mr Trump said: "This is a humanitarian crisis, a crisis of the heart and a crisis of the soul."
He added: "The federal government remains shut down for one reason and one reason only: because Democrats will not fund border security."
The Republican president wants $5.7bn (£4.5bn) to build a steel barrier, which would deliver on his signature campaign pledge, but Democrats are adamantly opposed to giving him the funds.
The current closure of a quarter of federal agencies is the second-longest in history, leaving hundreds of thousands of government workers unpaid.
Aiming to keep up the pressure, President Trump will seek to rally ruffled Republican senators at Capitol Hill on Wednesday, before heading to the border on Thursday.