U.S. President Donald Trump vowed Tuesday he would not reopen the government until he gets five billion U.S. dollars to fund his border wall, as the partial government shutdown dragged into a fourth day.

Trump's demand for a physical barrier on the U.S.-Mexico border – a pillar of his election platform – has been rejected by Democrats and some Republicans.

In retaliation, Trump refused last week to sign a wider spending bill, temporarily stripping funding from swaths of the government.

"I can't tell you when the government is going to reopen,” Trump said, speaking after a Christmas Day video conference with U.S. troops serving abroad. “I can tell you it's not going to reopen until we have a wall, a fence, whatever they'd like to call it. I'll call it whatever they want, but it's all the same thing. It's a barrier from people pouring into the country, from drugs.”

He added: “If you don't have that (the wall), then we're just not opening.”

Trump reaffirmed a claim made on Twitter Monday that he had approved a contract for the construction of 115 miles (185 kilometers) of wall in Texas, although the White House has not offered any details on the project.

He said he would visit that stretch of the border "at the end of January for the start of construction." 

"It's going to be built, hopefully rapidly," he said.

The president said he aimed to have a barrier stretching across 500 to 550 miles of the 2,000-mile border, and "to have it either renovated or brand new by election time."

"It's going to all work out," he said, adding that some furloughed federal workers also favor the construction of border wall Trump says will discourage illegal immigration.

Top Senate Democrat Chuck Schumer said at the weekend the president "must abandon the wall, plain and simple" to reopen the government.

(Top image: U.S. President Donald Trump holds a video call with U.S. military service members in the Oval Office on Christmas morning in Washington, U.S., December 25, 2018. /VCG Photo)