Trump: 'Who pays' for Obama's appearance with Clinton?

Donald TrumpDonald TrumpPoll: More people view NATO favorably EPA chief jabs California’s environment push David Letterman: ‘Makes me sick’ that Trump represents us MORE is criticizing President Obama's use of Air Force One to travel to a campaign event in North Carolina on Tuesday with Hillary ClintonHillary Rodham ClintonHannity: I won't discuss Seth Rich story for now "out of respect for the family" Clinton slams Trump's budget: 'An unimaginable level of cruelty' Trump’s crisis of legitimacy MORE.

“Who pays?" Trump asked late Monday on Twitter, noting that Clinton will fly with Obama.

A White House official told a Time magazine reporter that the Obama administration, like previous administrations, follows “all rules and regulations to ensure that the [Democratic National Committee] or other relevant political committee pays what is required for the President to travel to political events.”

Clinton and Obama will appear together for the first time on the campaign trail in Charlotte, N.C. Trump also has an appearance set in North Carolina on Tuesday, in Raleigh.

Trump on Tuesday called the use of Air Force One a "total disgrace."

This report was updated on July 5 at 7:18 a.m.