Senate Minority Leader Chuck Schumer and House Minority Leader Nancy Pelosi, held a joint press conference on Thursday evening.

"President Trump is throwing a temper tantrum and creating a Trump shutdown," Schumer said.

A partial government shutdown is looming — nine federal agencies may not be funded going in to the holidays — if a funding bill is not passed by the end of Friday.

The conference came shortly after Secretary of Defense Jim Mattis submitted his letter of resignation over the president's decision to pull US troops out of Syria.

Trump signaled this morning that he won't sign a bill if it does not include roughly $5 billion in funding for a wall at the southern border.

On Thursday night, the House of Representatives passed a stopgap bill that includes $5.7 billion in funding for the border wall. It's unlikely to pass the Senate.

Democratic leaders, Senate Minority Leader Chuck Schumer and House Minority Leader Nancy Pelosi, held a joint press conference on Thursday evening, following the announcement of Secretary of Defense James Mattis' resignation.

During the conference, Schumer and Pelosi discussed a looming government shutdown and Mattis leaving the administration.

"Today's events have made one thing clear, President Trump is plunging the country into chaos," Schumer said. "The stock market is down another 500 points. General Mattis stepping down — we know he has real disagreements with the president on Syria and on the wall. And now President Trump is throwing a temper tantrum and creating a Trump shutdown of the government."

Senate Minority Leader Chuck Schumer (D-NY) and House Minority Leader Nancy Pelosi (D-CA) speak to the media ahead of a possible partial government shut down in Washington, U.S., December 20, 2018. REUTERS/Joshua Roberts

On Wednesday night, the Senate passed a bipartisan stopgap bill unanimously by voice to fund the government through February. It was thought that President Trump would sign it — even without funding for the wall — to avoid a shutdown.

However, on Thursday, after being attacked by staunch conservatives (pundits and lawmakers alike) who favor the wall, Trump indicated to House Speaker Paul Ryan, that he would not sign a bill without funding for border security.

"We protect nations all over the world, but Democrats are unwilling to protect our nation," White House Press Secretary Sarah Huckabee Sanders said in a statement on Thursday. "We urgently need funding for border security and that includes a wall."

The wall was one of Trump's divisive campaign promises. A stopgap bill without border wall funding would push the spending fight to the new year, when Democrats will have a majority in the House and Pelosi will likely be Speaker of the House, making it harder to pass funding for the border wall.

On Thursday night, House Republicans passed a stopgap bill that included $5.7 billion for the wall. It is unlikely to pass in the Senate where it needs 60 votes to pass.

If the government shuts down, nine government agencies — the US Treasury, along with the departments of Agriculture, Homeland Security, the Interior, State, Housing and Urban Development, Transportation, Commerce and Justice — will not be funded. Government workers who are deemed "essential" will still have to work over the holidays without pay, including air traffic controllers, railroad safety inspectors, TSA agents, during the busy holiday travel season, and Customs and Border Protection agents, The Times reports.

"The bottom line is simple," Schumer said. "The Trump temper tantrum will shut down the government, but it will not get him his wall."