WASHINGTON — President Trump’s evolving definition of a border wall animated negotiations to end a partial government shutdown on Sunday, while House Democrats moved to increase pressure on the president by vowing to pass individual bills to reopen targeted departments that handle critical functions like tax refunds and food stamps.

“I informed my folks to say that we’ll build a steel barrier,” Mr. Trump told reporters after returning to the White House from a senior staff meeting at Camp David. He added of the Democrats, “They don’t like concrete, so we’ll give them steel.”

The president characterized the second day of talks between Vice President Mike Pence and Democratic congressional aides as “productive” after saying earlier in the day that he did not anticipate much progress. But Mr. Trump also said that, if no deal could be reached over his demand for $5.7 billion for the border wall, he was still considering using “emergency” authority to build the barrier with other government funds.

For their part, Democrats said there was no progress as the shutdown entered its 16th day, and asked again that the government be reopened before negotiations on border security money begin.