President Trump says he’s willing to shut down the government if Congress doesn’t send him a bill over the next 10 days approving $5 billion for his long-promised wall on the U.S.-Mexico border.

Congress must pass a spending package before Dec. 8, or the government will shut down. The flashpoint for a possible shuttering is Trump’s demand for $5 billion for a border wall, a price Democrats are rejecting.

Speaking to Politico on Monday, the president said he would "totally be willing" to close the government if he doesn’t get the wall funding. As for his $5 billion demand, Trump told the outlet, "I am firm."

On Tuesday, Senate Democratic leader Chuck Schumer of New York told reporters that Democrats are willing to agree to $1.6 billion for border security, but not Trump’s figure, saying, “If there is any shutdown, it’s on President Trump’s back.”

The vow from Trump comes amid recent clashes on the border between border agents and caravan migrants. On Sunday, U.S. agents used tear gas after they said rocks were thrown at them by people trying to enter the United States illegally.

The drama seemingly has only emboldened Trump in his push for more border security.

“I will tell you, politically speaking, that issue is a total winner,” Trump told Politico. “People look at the border, they look at the rush to the police, they look at the rock throwers and really hurting three people, three very brave border patrol folks -- I think that it's a tremendous issue, but much more importantly, is really needed. So we have to have border security."

There’s a lot of pressure on the president to make good on his campaign promise of a border wall, even if it means tempting a shutdown. Republicans – who lose control of the House in January – view the December standoff over the wall as the last chance to secure its funding.

Border wall advocates want a long-term investment in the wall. They fear the money will disappear next year unless they secure it now. But there’s some belief that Trump could compromise on the wall and say he secured a down payment.

That would tee up a fight with House Democrats next year -- and fighting with Democrats over the wall as he nears the 2020 presidential campaign could help the president appeal to his base if the wall isn’t completed.