Former President Donald Trump's plane was diverted Friday making a landing in Billings, Montana, due to a mechanical issue, an airport spokesperson and sources told ABC News.

Trump was en route to a campaign event at Brick Breeden Fieldhouse in Bozeman, Montana, scheduled for later in the night.

The situation was not an emergency, sources close to the former president told ABC News.

The sources and airport spokesperson say Trump continued to Bozeman on a smaller private jet.

-ABC News' John Santucci, Katherine Faulders, Luke Barr and Clara Mcmichael

Former Vice President Mike Pence reiterated Friday that he would not vote for his successor despite not supporting former President Donald Trump.

"Let me go on the record here at the gathering: I could never vote for Kamala Harris as president of the United States, or Tim Walz, as her running mate. Period," Pence said during an on-camera interview with conservative radio host Erick Erickson.

Pence defended his decision to not support Trump, citing several issues including "marginalizing the right-to-life in our party, as we saw on the national platform."

"I cannot endorse President Trump's continuing assertion that I should have set aside my oath to support and defend the Constitution and acted in a way that would have overturned the election in January of 2021," Pence added.

The former vice president did say he was grateful that Trump was not seriously hurt during the attempted assassination during a rally in Pennsylvania last month.

"Karen and I, we were in a plane, we had just landed, and I had got a text from someone watching it in real time. It took my breath away," he said, referring to his wife. "I truly admired the way the president stood up and raised his fist and walked off that stage."

-ABC News' Brittany Shepherd

President Biden and Vice President Harris will hold a joint event in Maryland on Thursday, Aug. 15, according to the White House.

They will discuss "the progress they are making to lower costs for the American people," the White House said.

Meanwhile, ahead of visits this weekend to Arizona and Nevada, the Harris campaign is touting what it called its "historic ground game advantage" in the two battleground states.

In a memo, the campaign also notes the elevated importance in Arizona and Nevada of reproductive freedom, as abortion-related ballot measures will be in place in each state this fall.

"Vice President Kamala Harris and Governor Tim Walz's momentum across the battlegrounds is real and will be on full display in Arizona and Nevada, where we've built massive coordinated campaigns as Trump has almost no presence whatsoever," the memo read. "Our campaign will continue our work to reach the diverse voters who power our victories in the Southwest, highlighting the stakes of the race for reproductive rights and the Vice President's leadership to secure the border."

Former President Donald Trump is set to hold a campaign rally in Bozeman, Montana, on Friday.

Vice President Kamala Harris will not be joining former President Donald Trump on Fox News' debate stage on Sept. 4, a Harris campaign official told ABC News.

The official said Harris agreeing to future debates is contingent on Trump showing up and "keeping his word" to the Sept. 10 debate, hosted by ABC News.

Harris' campaign is willing to have conversations about future debates, but they must be scheduled after Sept. 10, according to the official.