Senator Bernie Sanders plans to meet with several of his most important supporters and advisers in Burlington, Vt., on Sunday, as he faces increasing pressure to drop out of the Democratic presidential race.

The Vermont senator and his wife, Jane, will both attend the meeting that will center, in part, on the state of the race.

“He and Jane invited a couple dozen key supporters from around the country to come to Burlington,” Michael Briggs, a spokesman for Mr. Sanders, said. “It will be a broad-ranging discussion.”

While Hillary Clinton now has enough delegates to clinch the nomination, Mr. Sanders has refused to concede.