The comments represent a departure from congressional leaders who hope to punt a standoff on funding for the border wall until after the midterm elections.
"We have to protect our borders," Trump stressed. "If we don't protect our borders, our country won't be a country so if it has to do with border security, I'm willing to do what has to be done."
Earlier Wednesday, House Speaker Paul Ryan insisted that Trump was on the same page as congressional leaders, despite repeated campaign rhetoric during the summer to the contrary.
"That's not in anyone's interest, and he knows that," Ryan, R-Wis., said of a possible shutdown. "I think the results will prove itself."
But after the president expressed ambivalence over his position later Wednesday, Ryan refused to comment as he returned to the Capitol following the meeting.
House Majority Whip Steve Scalise, however, told reporters it was a "productive meeting."
"Well clearly the president campaigned on securing the border and building the wall and we strongly support those efforts," Scalise, R-La., said. "There is some wall being built. Obviously there’s a lot more wall that we want to see built."
As the deadline to pass a funding bill rapidly approaches, Scalise emphasized that Congress will grind forward this month on other appropriations bills ahead of an anticipated short-term continuing resolution that funds the government into December and the lame duck session of Congress.
"I’m confident that the House is working to make sure that we properly fund the military," Scalise said. "And there are a number of other bills to fund different parts of the government where we have agreement between the House and the Senate, and we’re trying to get all those bills to the president’s desk."
Current funding expires at the end of the day on September 30.
ABC News' Jordyn Phelps contributed to this report.