WASHINGTON — President Trump proclaimed on Thursday that without funding for his wall at the southwestern border, the panel of lawmakers negotiating a broad compromise on border security would be “wasting their time,” issuing what appeared to be an ultimatum even as lawmakers pleaded for a chance to reach a deal that would head off another shutdown.

“Without a wall, it doesn’t work,” Mr. Trump told reporters in the Oval Office. “I’m not saying this as a Republican, I’m not saying it as anything other than a fact stater.”

“If you don’t have a wall,” he added, “they’re all just wasting their time.”

And in an interview with The New York Times on Thursday, the president indicated that he was prepared to move forward without lawmakers, saying that he had “set the stage for doing what I’m going to do.” He declined to directly say whether he planned to declare a national emergency to build a wall.

[Read the New York Times interview with President Trump.]

The comments came as 17 House and Senate lawmakers from both parties struggled to reach a bipartisan border deal before Feb. 15, when much of the government again runs out of money. Republican leaders, especially in the Senate, have made it clear that they do not want to suffer through another debilitating shutdown, and senators asked the president to give them room to work.