United States (U.S.) President, Donald Trump, threatened on Sunday to shut down the government if Congress does not fund construction of a wall along the U.S.-Mexican border to thwart illegal immigration.

The U.S. leader claimed opposition Democrats need to give him “the votes for Border Security, which includes the Wall!” and other tougher national immigration policy changes. But it was a splintered Republican majority bloc of lawmakers, along with unified Democratic opposition, that twice in recent weeks rejected immigration changes Trump supported.

Trump, in a Twitter comment, called for the U.S. to “finally go to system of Immigration based on MERIT! We need great people coming into our Country!

According to VOA, Trump’s call for a wall, a favorite vow from his 2016 presidential campaign, would likely cost more than $20 billion, but Congress so far has allocated only $1.5 billion for extra border security. Democrats have often assailed the wall proposal, along with some Republicans. Trump, meanwhile has long claimed Mexico would pay for it, but Mexican leaders have adamantly said they would not, leaving the U.S. president to plead with Congress to fund it.

Trump’s threatened government shutdown would come as spending authorization runs out again at the end of the current fiscal year at the end of September, about five weeks before nationwide congressional elections on November 6. U.S. lawmakers usually, but not always, reach a spending accord shortly before funding runs out or after a short funding hiatus, as occurred last year.

As he continued to lobby for a border wall, Trump issued a new warning to migrants looking to illegally cross the Mexican border into the United States, saying they would face “consequences” even if they are accompanied by children.

He said that many of the border crossers “are just using children for their own sinister purposes.”

Trump’s latest attacks against U.S. immigrants entering the U.S. illegally – most of them from Guatemala, El Salvador and Honduras – comes as his administration continues to deal with the fallout of his “zero tolerance” policy of weeks ago in which more than 2,500 children were separated from their parents as they crossed into the United States.

A month ago, Trump ended the breakup of families. Under a court order, the U.S. government reunited by last Thursday more than 1,800 children with their parents, other family members already in the U.S. or sponsor households.

But more than 700 more are awaiting reunification or can’t, for one reason or another, be reunified. A total of 431 parents were deported without their children or left of their own accord. Nearly 100 children have parents who can’t be located.

Dana Sabraw, a U.S. judge in San Diego, California, who is overseeing the reunification of families, said the government deserves “great credit” for the reunification of the 1,800 children with their parents or other family members. But he also said “the government is at fault for losing several hundred parents in the process and that’s where we go next.”