© AP Photo/Andrew Harnik
President Donald Trump speaks during a news conference in the James Brady Press Briefing Room at the White House, Monday, Aug. 31, 2020, in Washington.
President Trump said that Democratic presidential nominee Joseph R. Biden is essentially a "puppet" controlled by shadowy figures lurking in the dark.

He also suggested that a planned attack on the Republican National Convention might have been thwarted but declined to go into detail.

"He's a weak person. He's controlled like a puppet," Mr. Trump said of Mr. Biden in an interview that aired on Fox News Monday evening.

Asked who is "pulling Biden's strings," Mr. Trump said: "People that you've never heard of. People that are in the dark shadows."

"They're people that are controlling the streets," he said. "We had somebody get on a plane from a certain city this weekend, and in the plane it was almost completely loaded with thugs wearing these dark uniforms, black uniforms with gear and this and that. They're on a plane."

Asked where that was, Mr. Trump said it's under investigation.

"But they came from a certain city, and this person was coming to the Republican National Convention, and there were like seven people on the plane like this person, and then a lot of people were on the plane to do big damage," he said.