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Trump tweeted Friday that if "Obstructionist Democrats" don't give him the billions of dollars he is asking for he will "close the Southern Border entirely."
"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," the president tweeted. "Hard to believe there was a Congress & President who would approve!"
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. Hard to believe there was a Congress & President who would approve!— Donald J. Trump (@realDonaldTrump) December 28, 2018
Trump added that closing the southern border, which would dramatically impact trade and people living on the border, would be a "profit making operation."
Mick Mulvaney, the incoming acting chief of staff, told reporters on Friday that the president is threatening to shut down the border because "it's the only way we can get the Democrats' attention."
Earlier on Fox News, Mulvaney said the president canceled his New Year's Eve plans at Mar-a-Lago in Palm Beach, Florida, to stay in Washington for potential negotiations.
"We are here and they know where to find us," Mulvaney said, adding, "The discussions have broken down, we expect this to go on for a while, we expect to manage it."
"We could be in this for the long haul," Mulvaney said.
The president also threatened that he would cut off aid to three Central American countries -- Guatemala, Honduras and El Salvador -- for being the source of the migrant caravans. Reports emerged that a new caravan from Honduras is preparing to leave for Mexico.
"Honduras, Guatemala and El Salvador are doing nothing for the United States but taking our money. Word is that a new Caravan is forming in Honduras and they are doing nothing about it. We will be cutting off all aid to these 3 countries - taking advantage of U.S. for years!” Trump tweeted.
The president has threatened to cut off aid before. The administration, however, recently struck a deal with Mexico to send billions of dollars in aid to Central American countries to curb migration.
"We are in the posture of ensuring that our programs are achieving their objectives and I think this is an ongoing review and I think there will probably be more of it and more to come," a senior State Department official said.
The government has been partially shut down since last week over an impasse between Trump and Democrats over funding for a proposed security wall along the U.S.-Mexico border. The government shutdown, which has kept hundreds of thousands of federal employees out of work, is expected to extend into the new year.
On Thursday, the Senate was in session for only four minutes after lawmakers didn't show up. They aren't expected in Washington again until the middle of next week.
Approximately 420,000 federal employees have been forced to work without pay during the holidays and another 380,000 are furloughed.
The deadlock also comes as a second immigrant child died at the border this month.
Felipe Alonzo-Gomez, an 8-year-old Guatemalan boy, died while in U.S. Customs and Border Protection custody earlier this week.
On Dec. 8, a 7-year-old girl named Jakelin Caal Maquin, also died in Border Patrol custody.
ABC News' Elizabeth McLaughlin contributed to this report.