It's his determination to keep that promise that has led to the current government shutdown.
After a weekend and two holiday days for federal employees, Wednesday was the first regularly scheduled workday affected by the shutdown.
"It's going to be built, hopefully rapidly", he said.
As the government shutdown entered its fourth day and expected to stretch at least well into the week, the president said the US must have "a wall, a fence, whatever they want to call it". During prior shutdowns, lawmakers generally have voted to retroactively pay all employees - those who worked and those who were furloughed - after the government re-opens.
The shutdown is entering its fifth day as the White House and Congress show very little signs of movement.
"Whatever it takes", Trump said.
Democrats have supported including an additional US$1.3 billion in border security funding, at one point agreeing to an additional US$1.6 billion during negotiations with congressional Republicans.
So far, the public and federal workers have largely been spared inconvenience and hardship because government is closed on weekends and federal employees were excused from work on Christmas Eve and Christmas, a federal holiday.
Led coalition reports recent air strikes on ISIS in Syria
In a widely circulated tweet, he said the USA "has ended the ridiculous 230 Million Dollar yearly development payment to Syria ". And Kalin vowed that there was "no question of a step backwards, vulnerability or a slowdown in the fight against Daesh (IS)".
"I can't tell you when the government's going to be open.
I can tell you it's not going to be open until we have a wall, a fence, whatever they'd like to call it", Trump said in the Oval Office after a video conference with USA troops, who are stationed overseas.
Although Trump had said he would be "proud" to shut down the government until the wall could be fully funded, he has since tried to shift the blame to Democrats - specifically for not supporting a House-passed bill that includes $5 billion for the funding wall. Park roads and grounds at Mount Rushmore National Memorial remain open to visitors, but there are no National Park Service-provided visitor services at Mount Rushmore during the government shutdown.
The shutdown that began on Saturday - the third of 2018 - caused a lapse in funding for nine of 15 Cabinet-level departments and dozens of agencies, including the departments of Homeland Security, Transportation, Interior, Agriculture, State and Justice.
Mr Trump claimed that many of these workers "have said to me and communicated "stay out until you get the funding for the wall". While the caravan of thousands approached our borders, Democrats argued that it was no more than a spontaneous effort by oppressed women and children seeking a safe harbor.
"Do I think the dynamics are going to change much come the new year?" Many are on the job but must wait until after the shutdown to be paid again.
Roughly 44,000 U.S. Coast Guard employees are considered essential, and will report to work this week without pay, with another 6,000 furloughed.