Pedro Mario Burelli, a veteran Venezuelan political operative and an opponent of Mr. Maduro’s movement, called the visit part of an effort to “freak him out” — to scare Mr. Maduro into believing that the global political tide is increasingly turning against him.

Edmundo González Urrutia is trying to bolster international support before Venezuelan strongman Nicolás Maduro is sworn in Friday.

"We had a long, fruitful and cordial conversation with President Biden and his team," Gonzalez told journalists after the meeting at the White House. "Our team is in contact with the team of President Trump.