Mulvaney said Trump is willing to shut down the border, despite the economic hit as $558 billion worth of goods flowed across the border previous year, because "all options are on the table" and "it's the only way we can get the Democrats' attention". And he and his aides made clear she will be a focal point of his expected 2020 re-election campaign.
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.
Trump's demand for money to build the border wall and Democrats' refusal to give him what he wants has caused a partial government shutdown that is almost a week old.
In Mexico, President Andres Manuel Lopez Obrador sidestepped Trump's threat, telling journalists: "We don't want to be imprudent and we don't think we should get into this".
FILE - House Minority Leader Nancy Pelosi of Calif., right, accompanied by Senate Minority Leader Sen.
A spokesman for U.S. Senate Democratic leader Chuck Schumer said on Thursday that Republicans and Democrats were still very far apart in efforts to resolve the partial government shutdown, which started on Saturday.
In a joint statement, Senate Minority Leader Chuck Schumer of NY and presumed incoming House Speaker Nancy Pelosi of California said, "The president wanted the shutdown, but seems not to know how to get himself out of it".
"The more we're hearing, it is Nancy Pelosi preventing that from happening", he said.
Republicans now control both houses of Congress and the White House, but in one week, Democrats will take over in the House while Republicans will add two seats to their current Senate advantage. During an interview Friday, Sanders criticized Democrats for refusing to budge on the issue of immigration and said they have completely left the negotiation table.
The president tweeted the contention that the ongoing shutdown "isn't about the Wall", adding: "This is only about the Dems not letting Donald Trump & the Republicans have a win".
The next morning, the president was back on Twitter threatening Democrats - less than a week away from being forced to negotiate with Pelosi and a House Democratic majority to re-open nine Cabinet agencies and a list of smaller federal offices.
"(Senate Minority Leader) Chuck Schumer voted for border security in 2006.
Mr. Trump also expressed disbelief that the U.S.in his view has struggled for so long with porous borders and weak laws that foster rampant illegal immigration.
In a befuddling series of tweets Friday, President Trump appeared to threaten both the Democrats and USA trade relations with Mexico when he suggested he would close the southern border.