"Either we build (finish) the Wall or we close the Border," the US president tweeted after nearly a week of deadlock in Washington over the federal budget.
Confirming the threat to close the border was real, the White House said negotiations with Congress had stalled.The dispute has caused a partial US government shutdown.
Hundreds of thousands of federal employees are either on unpaid leave or continue to work but do not know when they will be paid.Both Congress chambers met for just a few minutes on Thursday but took no steps to end the closure. The House and Senate will now meet again on Monday.
Later in the week, a new House will be sworn in, dominated by opposition Democrats who won the mid-term elections last month, but Mr Trump's Republicans will retain the Senate with a slightly larger majority.
In October Mr Trump made a similar threat to close the southern US border when demanding action from Latin American governments to stop migrants, in what has become known as the caravan, trying to cross into the US illegally.
What exactly did Trump say?
"We will be forced to close the Southern Border entirely if the Obstructionist Democrats do not give us the money to finish the Wall & also change the ridiculous immigration laws that our Country is saddled with," he tweeted on Friday.
He is seeking $5bn (£4bn) to cover the cost of the wall but Democrats and some within Mr Trump's own party insist they will not approve it.
Mr Trump argued on Friday that the US had lost out to Mexico by $75bn a year under the North American Free Trade Agreement (Nafta), which he replaced with a new deal with Mexico and Canada last month. - BBC