Trump says he's made his veep decision in his 'mind' and the person will be at Thursday's debate

• Donald Trump says he's decided his vice presidential pick but hasn't revealed the name.
• Trump hinted the chosen running mate will attend Thursday's debate against Biden.
• Trump said he plans to announce his pick around the Republican National Convention, which begins July 15.

Donald Trump says he's already decided who his running mate will be but that nobody else knows who it is.

At a stop along the campaign trail in Philadelphia on Saturday, NBC News asked Trump if he knows yet who he'll pick as his vice presidential candidate.

"In my mind, yeah," the former president answered.

He said that his pick will be at the presidential debate against incumbent Joe Biden on Thursday. "They'll be there," he told NBC. "I think we have a lot of people coming."

But not even the VP knows yet they've been chosen in Trump.

Trump was asked if his pick knows they've been selected, and Trump responded, "No, nobody knows," according to Fox News.

Trump has been considering four top contenders for the nomination: North Dakota Gov. Doug Burgum, Sen. Marco Rubio of Florida, Sen. JD Vance of Ohio, and Sen. Tim Scott of South Carolina.

Burgum and Vance have recently emerged as finalists from that list, sources told NBC News last week. Sources told the outlet that Rubio is also still a possibility, but the issue with Rubio is that either he or Trump would likely need to establish residency outside of Florida as both candidates hailing from the same state could pose a problem if the election is a close call.

Though the mystery running mate is expected to be present at the debate, their selection will most likely not be publicly announced at or ahead of the debate, according to Trump.

Trump told NBC News he plans to make the VP announcement "right around the convention," where he is expected to receive his party's formal nomination. The Republican National Convention begins in Milwaukee on July 15 and runs until July 18.

"Maybe a little before, but could be at the convention," Trump said. "But we'll have some great people."